diff --git a/.travis.yml b/.travis.yml
index d81b6fa..4666146 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -3,19 +3,26 @@ arch:
   - amd64
   - ppc64le
 python:
-  - "3.4"
   - "3.5"
   - "3.6"
   - "3.7"
   - "3.8"
   - "3.9"
   - "pypy3"
-# Disable unsuported version  pypy for ppc64le
+# Disable unsupported version  pypy for ppc64le
 jobs:
   exclude:
   - arch: ppc64le
     python: pypy3
 
+matrix:
+  include:
+    - python: 3.9
+      install:
+        - pip install mypy
+      script:
+        - mypy --strict idna/
+
 install:
   - pip install .
 script:
diff --git a/MANIFEST.in b/MANIFEST.in
index 66a19d4..3d746f6 100644
--- a/MANIFEST.in
+++ b/MANIFEST.in
@@ -1,7 +1,6 @@
 include *.rst
 include LICENSE.md
 include idna/py.typed
-recursive-include idna *.pyi
 recursive-include tools *
 recursive-exclude tools *.pyc
 recursive-include tests *
diff --git a/idna/__init__.py b/idna/__init__.py
index 338e170..a40eeaf 100644
--- a/idna/__init__.py
+++ b/idna/__init__.py
@@ -12,7 +12,6 @@
     check_nfc,
     decode,
     encode,
-    intranges_contain,
     ulabel,
     uts46_remap,
     valid_contextj,
@@ -20,6 +19,7 @@
     valid_label_length,
     valid_string_length,
 )
+from .intranges import intranges_contain
 
 __all__ = [
     "IDNABidiError",
diff --git a/idna/codec.py b/idna/codec.py
index 30fe72f..080f22a 100644
--- a/idna/codec.py
+++ b/idna/codec.py
@@ -1,23 +1,24 @@
 from .core import encode, decode, alabel, ulabel, IDNAError
 import codecs
 import re
+from typing import Tuple, Optional
 
 _unicode_dots_re = re.compile('[\u002e\u3002\uff0e\uff61]')
 
 class Codec(codecs.Codec):
 
     def encode(self, data, errors='strict'):
-
+        # type: (str, str) -> Tuple[bytes, int]
         if errors != 'strict':
             raise IDNAError('Unsupported error handling \"{}\"'.format(errors))
 
         if not data:
-            return "", 0
+            return b"", 0
 
         return encode(data), len(data)
 
     def decode(self, data, errors='strict'):
-
+        # type: (bytes, str) -> Tuple[str, int]
         if errors != 'strict':
             raise IDNAError('Unsupported error handling \"{}\"'.format(errors))
 
@@ -27,12 +28,13 @@ def decode(self, data, errors='strict'):
         return decode(data), len(data)
 
 class IncrementalEncoder(codecs.BufferedIncrementalEncoder):
-    def _buffer_encode(self, data, errors, final):
+    def _buffer_encode(self, data, errors, final):  # type: ignore
+        # type: (str, str, bool) -> Tuple[str, int]
         if errors != 'strict':
             raise IDNAError('Unsupported error handling \"{}\"'.format(errors))
 
         if not data:
-            return ('', 0)
+            return "", 0
 
         labels = _unicode_dots_re.split(data)
         trailing_dot = ''
@@ -55,12 +57,13 @@ def _buffer_encode(self, data, errors, final):
             size += len(label)
 
         # Join with U+002E
-        result = '.'.join(result) + trailing_dot
+        result_str = '.'.join(result) + trailing_dot  # type: ignore
         size += len(trailing_dot)
-        return (result, size)
+        return result_str, size
 
 class IncrementalDecoder(codecs.BufferedIncrementalDecoder):
-    def _buffer_decode(self, data, errors, final):
+    def _buffer_decode(self, data, errors, final):  # type: ignore
+        # type: (str, str, bool) -> Tuple[str, int]
         if errors != 'strict':
             raise IDNAError('Unsupported error handling \"{}\"'.format(errors))
 
@@ -87,22 +90,26 @@ def _buffer_decode(self, data, errors, final):
                 size += 1
             size += len(label)
 
-        result = '.'.join(result) + trailing_dot
+        result_str = '.'.join(result) + trailing_dot
         size += len(trailing_dot)
-        return (result, size)
+        return (result_str, size)
 
 
 class StreamWriter(Codec, codecs.StreamWriter):
     pass
 
+
 class StreamReader(Codec, codecs.StreamReader):
     pass
 
+
 def getregentry():
+    # type: () -> codecs.CodecInfo
+    # Compatibility as a search_function for codecs.register()
     return codecs.CodecInfo(
         name='idna',
-        encode=Codec().encode,
-        decode=Codec().decode,
+        encode=Codec().encode,  # type: ignore
+        decode=Codec().decode,  # type: ignore
         incrementalencoder=IncrementalEncoder,
         incrementaldecoder=IncrementalDecoder,
         streamwriter=StreamWriter,
diff --git a/idna/codec.pyi b/idna/codec.pyi
deleted file mode 100644
index 3726afc..0000000
--- a/idna/codec.pyi
+++ /dev/null
@@ -1,27 +0,0 @@
-import codecs
-from typing import Tuple
-
-class Codec(codecs.Codec):
-    def encode(self, data: str, errors: str = ...) -> Tuple[bytes, int]: ...
-    def decode(self, data: bytes, errors: str = ...) -> Tuple[str, int]: ...
-
-class IncrementalEncoder(codecs.BufferedIncrementalEncoder):
-    def _buffer_encode(  # type: ignore
-        self,
-        data: str,
-        errors: str,
-        final: bool
-    ) -> Tuple[str, int]: ...
-
-class IncrementalDecoder(codecs.BufferedIncrementalDecoder):
-    def _buffer_decode(  # type: ignore
-        self,
-        data: str,
-        errors: str,
-        final: bool
-    ) -> Tuple[str, int]: ...
-
-class StreamWriter(Codec, codecs.StreamWriter): ...
-class StreamReader(Codec, codecs.StreamReader): ...
-
-def getregentry() -> codecs.CodecInfo: ...
diff --git a/idna/compat.py b/idna/compat.py
index 2e622d6..dc896c7 100644
--- a/idna/compat.py
+++ b/idna/compat.py
@@ -1,12 +1,16 @@
 from .core import *
 from .codec import *
+from typing import Any, Union
 
 def ToASCII(label):
+    # type: (str) -> bytes
     return encode(label)
 
 def ToUnicode(label):
+    # type: (Union[bytes, bytearray]) -> str
     return decode(label)
 
 def nameprep(s):
+    # type: (Any) -> None
     raise NotImplementedError('IDNA 2008 does not utilise nameprep protocol')
 
diff --git a/idna/compat.pyi b/idna/compat.pyi
deleted file mode 100644
index 44677a6..0000000
--- a/idna/compat.pyi
+++ /dev/null
@@ -1,5 +0,0 @@
-from typing import Any
-
-def ToASCII(label: str) -> bytes: ...
-def ToUnicode(label: bytes) -> str: ...
-def nameprep(s: Any) -> None: ...
diff --git a/idna/core.py b/idna/core.py
index 2c193d6..d605129 100644
--- a/idna/core.py
+++ b/idna/core.py
@@ -2,7 +2,7 @@
 import bisect
 import unicodedata
 import re
-import sys
+from typing import Union, Optional
 from .intranges import intranges_contain
 
 _virama_combining_class = 9
@@ -30,6 +30,7 @@ class InvalidCodepointContext(IDNAError):
 
 
 def _combining_class(cp):
+    # type: (int) -> int
     v = unicodedata.combining(chr(cp))
     if v == 0:
         if not unicodedata.name(chr(cp)):
@@ -37,31 +38,34 @@ def _combining_class(cp):
     return v
 
 def _is_script(cp, script):
+    # type: (str, str) -> bool
     return intranges_contain(ord(cp), idnadata.scripts[script])
 
 def _punycode(s):
+    # type: (str) -> bytes
     return s.encode('punycode')
 
 def _unot(s):
+    # type: (int) -> str
     return 'U+{:04X}'.format(s)
 
 
 def valid_label_length(label):
-
+    # type: (Union[bytes, str]) -> bool
     if len(label) > 63:
         return False
     return True
 
 
 def valid_string_length(label, trailing_dot):
-
+    # type: (Union[bytes, str], bool) -> bool
     if len(label) > (254 if trailing_dot else 253):
         return False
     return True
 
 
 def check_bidi(label, check_ltr=False):
-
+    # type: (str, bool) -> bool
     # Bidi rules should only be applied if string contains RTL characters
     bidi_label = False
     for (idx, cp) in enumerate(label, 1):
@@ -84,7 +88,7 @@ def check_bidi(label, check_ltr=False):
         raise IDNABidiError('First codepoint in label {} must be directionality L, R or AL'.format(repr(label)))
 
     valid_ending = False
-    number_type = False
+    number_type = None  # type: Optional[str]
     for (idx, cp) in enumerate(label, 1):
         direction = unicodedata.bidirectional(cp)
 
@@ -121,14 +125,14 @@ def check_bidi(label, check_ltr=False):
 
 
 def check_initial_combiner(label):
-
+    # type: (str) -> bool
     if unicodedata.category(label[0])[0] == 'M':
         raise IDNAError('Label begins with an illegal combining character')
     return True
 
 
 def check_hyphen_ok(label):
-
+    # type: (str) -> bool
     if label[2:4] == '--':
         raise IDNAError('Label has disallowed hyphens in 3rd and 4th position')
     if label[0] == '-' or label[-1] == '-':
@@ -137,13 +141,13 @@ def check_hyphen_ok(label):
 
 
 def check_nfc(label):
-
+    # type: (str) -> None
     if unicodedata.normalize('NFC', label) != label:
         raise IDNAError('Label must be in Normalization Form C')
 
 
 def valid_contextj(label, pos):
-
+    # type: (str, int) -> bool
     cp_value = ord(label[pos])
 
     if cp_value == 0x200c:
@@ -187,7 +191,7 @@ def valid_contextj(label, pos):
 
 
 def valid_contexto(label, pos, exception=False):
-
+    # type: (str, int, bool) -> bool
     cp_value = ord(label[pos])
 
     if cp_value == 0x00b7:
@@ -226,9 +230,11 @@ def valid_contexto(label, pos, exception=False):
                 return False
         return True
 
+    return False
 
-def check_label(label):
 
+def check_label(label):
+    # type: (Union[str, bytes, bytearray]) -> None
     if isinstance(label, (bytes, bytearray)):
         label = label.decode('utf-8')
     if len(label) == 0:
@@ -260,13 +266,13 @@ def check_label(label):
 
 
 def alabel(label):
-
+    # type: (str) -> bytes
     try:
-        label = label.encode('ascii')
-        ulabel(label)
-        if not valid_label_length(label):
+        label_bytes = label.encode('ascii')
+        ulabel(label_bytes)
+        if not valid_label_length(label_bytes):
             raise IDNAError('Label too long')
-        return label
+        return label_bytes
     except UnicodeEncodeError:
         pass
 
@@ -275,51 +281,57 @@ def alabel(label):
 
     label = str(label)
     check_label(label)
-    label = _punycode(label)
-    label = _alabel_prefix + label
+    label_bytes = _punycode(label)
+    label_bytes = _alabel_prefix + label_bytes
 
-    if not valid_label_length(label):
+    if not valid_label_length(label_bytes):
         raise IDNAError('Label too long')
 
-    return label
+    return label_bytes
 
 
 def ulabel(label):
-
+    # type: (Union[str, bytes, bytearray]) -> str
     if not isinstance(label, (bytes, bytearray)):
         try:
-            label = label.encode('ascii')
+            label_bytes = label.encode('ascii')
         except UnicodeEncodeError:
             check_label(label)
             return label
+    else:
+        label_bytes = label
 
-    label = label.lower()
-    if label.startswith(_alabel_prefix):
-        label = label[len(_alabel_prefix):]
-        if not label:
+    label_bytes = label_bytes.lower()
+    if label_bytes.startswith(_alabel_prefix):
+        label_bytes = label_bytes[len(_alabel_prefix):]
+        if not label_bytes:
             raise IDNAError('Malformed A-label, no Punycode eligible content found')
-        if label.decode('ascii')[-1] == '-':
+        if label_bytes.decode('ascii')[-1] == '-':
             raise IDNAError('A-label must not end with a hyphen')
     else:
-        check_label(label)
-        return label.decode('ascii')
+        check_label(label_bytes)
+        return label_bytes.decode('ascii')
 
-    label = label.decode('punycode')
+    label = label_bytes.decode('punycode')
     check_label(label)
     return label
 
 
 def uts46_remap(domain, std3_rules=True, transitional=False):
+    # type: (str, bool, bool) -> str
     """Re-map the characters in the string according to UTS46 processing."""
     from .uts46data import uts46data
     output = ''
-    try:
-        for pos, char in enumerate(domain):
-            code_point = ord(char)
+
+    for pos, char in enumerate(domain):
+        code_point = ord(char)
+        try:
             uts46row = uts46data[code_point if code_point < 256 else
                 bisect.bisect_left(uts46data, (code_point, 'Z')) - 1]
             status = uts46row[1]
-            replacement = uts46row[2] if len(uts46row) == 3 else None
+            replacement = None  # type: Optional[str]
+            if len(uts46row) == 3:
+                replacement = uts46row[2]  # type: ignore
             if (status == 'V' or
                     (status == 'D' and not transitional) or
                     (status == '3' and not std3_rules and replacement is None)):
@@ -330,15 +342,16 @@ def uts46_remap(domain, std3_rules=True, transitional=False):
                 output += replacement
             elif status != 'I':
                 raise IndexError()
-        return unicodedata.normalize('NFC', output)
-    except IndexError:
-        raise InvalidCodepoint(
-            'Codepoint {} not allowed at position {} in {}'.format(
-            _unot(code_point), pos + 1, repr(domain)))
+        except IndexError:
+            raise InvalidCodepoint(
+                'Codepoint {} not allowed at position {} in {}'.format(
+                _unot(code_point), pos + 1, repr(domain)))
 
+    return unicodedata.normalize('NFC', output)
 
-def encode(s, strict=False, uts46=False, std3_rules=False, transitional=False):
 
+def encode(s, strict=False, uts46=False, std3_rules=False, transitional=False):
+    # type: (Union[str, bytes, bytearray], bool, bool, bool, bool) -> bytes
     if isinstance(s, (bytes, bytearray)):
         s = s.decode('ascii')
     if uts46:
@@ -369,7 +382,7 @@ def encode(s, strict=False, uts46=False, std3_rules=False, transitional=False):
 
 
 def decode(s, strict=False, uts46=False, std3_rules=False):
-
+    # type: (Union[str, bytes, bytearray], bool, bool, bool) -> str
     if isinstance(s, (bytes, bytearray)):
         s = s.decode('ascii')
     if uts46:
diff --git a/idna/core.pyi b/idna/core.pyi
deleted file mode 100644
index 5b8a4ac..0000000
--- a/idna/core.pyi
+++ /dev/null
@@ -1,39 +0,0 @@
-from typing import Union
-from .intranges import intranges_contain as intranges_contain  # noqa
-
-class IDNAError(UnicodeError): ...
-class IDNABidiError(IDNAError): ...
-class InvalidCodepoint(IDNAError): ...
-class InvalidCodepointContext(IDNAError): ...
-
-def _combining_class(cp: int) -> int: ...
-def _is_script(cp: str, script: str) -> bool: ...
-def _punycode(s: str) -> bytes: ...
-def _unot(s: int) -> str: ...
-def valid_label_length(label: Union[str, bytes]) -> bool: ...
-def valid_string_length(label: Union[str, bytes], trailing_dot: bool) -> bool: ...
-def check_bidi(label: str, check_ltr: bool = ...) -> bool: ...
-def check_initial_combiner(label: str) -> bool: ...
-def check_hyphen_ok(label: str) -> bool: ...
-def check_nfc(label: str) -> None: ...
-def valid_contextj(label: str, pos: int) -> bool: ...
-def valid_contexto(label: str, pos: int, exception: bool = False) -> bool: ...
-def check_label(label: Union[str, bytes, bytearray]) -> None: ...
-def alabel(label: str) -> bytes: ...
-def ulabel(label: Union[str, bytes, bytearray]) -> str: ...
-def uts46_remap(
-    domain: str, std3_rules: bool = ..., transitional: bool = ...
-) -> str: ...
-def encode(
-    s: Union[str, bytes, bytearray],
-    strict: bool = False,
-    uts46: bool = False,
-    std3_rules: bool = False,
-    transitional: bool = False,
-) -> bytes: ...
-def decode(
-    s: Union[str, bytes, bytearray],
-    strict: bool = ...,
-    uts46: bool = ...,
-    std3_rules: bool = ...,
-) -> str: ...
diff --git a/idna/idnadata.pyi b/idna/idnadata.pyi
deleted file mode 100644
index 691249f..0000000
--- a/idna/idnadata.pyi
+++ /dev/null
@@ -1,6 +0,0 @@
-from typing import Dict, Tuple
-
-__version__: str
-scripts: Dict[str, Tuple[int, ...]]
-joining_types: Dict[int, int]
-codepoint_classes: Dict[str, Tuple[int, ...]]
diff --git a/idna/intranges.py b/idna/intranges.py
index fa8a735..ee364a9 100644
--- a/idna/intranges.py
+++ b/idna/intranges.py
@@ -6,8 +6,10 @@
 """
 
 import bisect
+from typing import List, Tuple
 
 def intranges_from_list(list_):
+    # type: (List[int]) -> Tuple[int, ...]
     """Represent a list of integers as a sequence of ranges:
     ((start_0, end_0), (start_1, end_1), ...), such that the original
     integers are exactly those x such that start_i <= x < end_i for some i.
@@ -29,13 +31,16 @@ def intranges_from_list(list_):
     return tuple(ranges)
 
 def _encode_range(start, end):
+    # type: (int, int) -> int
     return (start << 32) | end
 
 def _decode_range(r):
+    # type: (int) -> Tuple[int, int]
     return (r >> 32), (r & ((1 << 32) - 1))
 
 
 def intranges_contain(int_, ranges):
+    # type: (int, Tuple[int, ...]) -> bool
     """Determine if `int_` falls into one of the ranges in `ranges`."""
     tuple_ = _encode_range(int_, 0)
     pos = bisect.bisect_left(ranges, tuple_)
diff --git a/idna/intranges.pyi b/idna/intranges.pyi
deleted file mode 100644
index cde4c23..0000000
--- a/idna/intranges.pyi
+++ /dev/null
@@ -1,6 +0,0 @@
-from typing import List, Tuple
-
-def intranges_from_list(list_: List[int]) -> Tuple[int, ...]: ...
-def _encode_range(start: int, end: int) -> int: ...
-def _decode_range(r: int) -> Tuple[int, int]: ...
-def intranges_contain(int_: int, ranges: Tuple[int, ...]) -> bool: ...
diff --git a/idna/package_data.pyi b/idna/package_data.pyi
deleted file mode 100644
index bda5b5a..0000000
--- a/idna/package_data.pyi
+++ /dev/null
@@ -1 +0,0 @@
-__version__: str
diff --git a/idna/uts46data.py b/idna/uts46data.py
index 8ae36cb..f382ce3 100644
--- a/idna/uts46data.py
+++ b/idna/uts46data.py
@@ -1,10 +1,13 @@
 # This file is automatically generated by tools/idna-data
 
+from typing import List, Tuple, Union
+
 """IDNA Mapping Table from UTS46."""
 
 
 __version__ = '13.0.0'
 def _seg_0():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x0, '3'),
     (0x1, '3'),
@@ -109,6 +112,7 @@ def _seg_0():
     ]
 
 def _seg_1():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x64, 'V'),
     (0x65, 'V'),
@@ -213,6 +217,7 @@ def _seg_1():
     ]
 
 def _seg_2():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0xC8, 'M', 'è'),
     (0xC9, 'M', 'é'),
@@ -317,6 +322,7 @@ def _seg_2():
     ]
 
 def _seg_3():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x12C, 'M', 'ĭ'),
     (0x12D, 'V'),
@@ -421,6 +427,7 @@ def _seg_3():
     ]
 
 def _seg_4():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x194, 'M', 'ɣ'),
     (0x195, 'V'),
@@ -525,6 +532,7 @@ def _seg_4():
     ]
 
 def _seg_5():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x20D, 'V'),
     (0x20E, 'M', 'ȏ'),
@@ -629,6 +637,7 @@ def _seg_5():
     ]
 
 def _seg_6():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x378, 'X'),
     (0x37A, '3', ' ι'),
@@ -733,6 +742,7 @@ def _seg_6():
     ]
 
 def _seg_7():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x403, 'M', 'ѓ'),
     (0x404, 'M', 'є'),
@@ -837,6 +847,7 @@ def _seg_7():
     ]
 
 def _seg_8():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x49E, 'M', 'ҟ'),
     (0x49F, 'V'),
@@ -941,6 +952,7 @@ def _seg_8():
     ]
 
 def _seg_9():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x503, 'V'),
     (0x504, 'M', 'ԅ'),
@@ -1045,6 +1057,7 @@ def _seg_9():
     ]
 
 def _seg_10():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x675, 'M', 'اٴ'),
     (0x676, 'M', 'وٴ'),
@@ -1149,6 +1162,7 @@ def _seg_10():
     ]
 
 def _seg_11():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0xA5C, 'V'),
     (0xA5D, 'X'),
@@ -1253,6 +1267,7 @@ def _seg_11():
     ]
 
 def _seg_12():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0xC29, 'X'),
     (0xC2A, 'V'),
@@ -1357,6 +1372,7 @@ def _seg_12():
     ]
 
 def _seg_13():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0xEBE, 'X'),
     (0xEC0, 'V'),
@@ -1461,6 +1477,7 @@ def _seg_13():
     ]
 
 def _seg_14():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x1316, 'X'),
     (0x1318, 'V'),
@@ -1565,6 +1582,7 @@ def _seg_14():
     ]
 
 def _seg_15():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x1C80, 'M', 'в'),
     (0x1C81, 'M', 'д'),
@@ -1669,6 +1687,7 @@ def _seg_15():
     ]
 
 def _seg_16():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x1D53, 'M', 'ɔ'),
     (0x1D54, 'M', 'ᴖ'),
@@ -1773,6 +1792,7 @@ def _seg_16():
     ]
 
 def _seg_17():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x1E21, 'V'),
     (0x1E22, 'M', 'ḣ'),
@@ -1877,6 +1897,7 @@ def _seg_17():
     ]
 
 def _seg_18():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x1E85, 'V'),
     (0x1E86, 'M', 'ẇ'),
@@ -1981,6 +2002,7 @@ def _seg_18():
     ]
 
 def _seg_19():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x1EEE, 'M', 'ữ'),
     (0x1EEF, 'V'),
@@ -2085,6 +2107,7 @@ def _seg_19():
     ]
 
 def _seg_20():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x1F85, 'M', 'ἅι'),
     (0x1F86, 'M', 'ἆι'),
@@ -2189,6 +2212,7 @@ def _seg_20():
     ]
 
 def _seg_21():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x1FF4, 'M', 'ώι'),
     (0x1FF5, 'X'),
@@ -2293,6 +2317,7 @@ def _seg_21():
     ]
 
 def _seg_22():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x2102, 'M', 'c'),
     (0x2103, 'M', '°c'),
@@ -2397,6 +2422,7 @@ def _seg_22():
     ]
 
 def _seg_23():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x217A, 'M', 'xi'),
     (0x217B, 'M', 'xii'),
@@ -2501,6 +2527,7 @@ def _seg_23():
     ]
 
 def _seg_24():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x24BA, 'M', 'e'),
     (0x24BB, 'M', 'f'),
@@ -2605,6 +2632,7 @@ def _seg_24():
     ]
 
 def _seg_25():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x2C26, 'M', 'ⱖ'),
     (0x2C27, 'M', 'ⱗ'),
@@ -2709,6 +2737,7 @@ def _seg_25():
     ]
 
 def _seg_26():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x2CBF, 'V'),
     (0x2CC0, 'M', 'ⳁ'),
@@ -2813,6 +2842,7 @@ def _seg_26():
     ]
 
 def _seg_27():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x2F12, 'M', '力'),
     (0x2F13, 'M', '勹'),
@@ -2917,6 +2947,7 @@ def _seg_27():
     ]
 
 def _seg_28():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x2F76, 'M', '米'),
     (0x2F77, 'M', '糸'),
@@ -3021,6 +3052,7 @@ def _seg_28():
     ]
 
 def _seg_29():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x3003, 'V'),
     (0x3036, 'M', '〒'),
@@ -3125,6 +3157,7 @@ def _seg_29():
     ]
 
 def _seg_30():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x3181, 'M', 'ᅌ'),
     (0x3182, 'M', 'ᇱ'),
@@ -3229,6 +3262,7 @@ def _seg_30():
     ]
 
 def _seg_31():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x3243, '3', '(至)'),
     (0x3244, 'M', '問'),
@@ -3333,6 +3367,7 @@ def _seg_31():
     ]
 
 def _seg_32():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x32AE, 'M', '資'),
     (0x32AF, 'M', '協'),
@@ -3437,6 +3472,7 @@ def _seg_32():
     ]
 
 def _seg_33():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x3312, 'M', 'キュリー'),
     (0x3313, 'M', 'ギルダー'),
@@ -3541,6 +3577,7 @@ def _seg_33():
     ]
 
 def _seg_34():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x3376, 'M', 'pc'),
     (0x3377, 'M', 'dm'),
@@ -3645,6 +3682,7 @@ def _seg_34():
     ]
 
 def _seg_35():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x33DA, 'M', 'pr'),
     (0x33DB, 'M', 'sr'),
@@ -3749,6 +3787,7 @@ def _seg_35():
     ]
 
 def _seg_36():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0xA688, 'M', 'ꚉ'),
     (0xA689, 'V'),
@@ -3853,6 +3892,7 @@ def _seg_36():
     ]
 
 def _seg_37():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0xA76F, 'V'),
     (0xA770, 'M', 'ꝯ'),
@@ -3957,6 +3997,7 @@ def _seg_37():
     ]
 
 def _seg_38():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0xA9DA, 'X'),
     (0xA9DE, 'V'),
@@ -4061,6 +4102,7 @@ def _seg_38():
     ]
 
 def _seg_39():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0xABB4, 'M', 'Ꮴ'),
     (0xABB5, 'M', 'Ꮵ'),
@@ -4165,6 +4207,7 @@ def _seg_39():
     ]
 
 def _seg_40():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0xF94F, 'M', '累'),
     (0xF950, 'M', '縷'),
@@ -4269,6 +4312,7 @@ def _seg_40():
     ]
 
 def _seg_41():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0xF9B3, 'M', '靈'),
     (0xF9B4, 'M', '領'),
@@ -4373,6 +4417,7 @@ def _seg_41():
     ]
 
 def _seg_42():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0xFA19, 'M', '神'),
     (0xFA1A, 'M', '祥'),
@@ -4477,6 +4522,7 @@ def _seg_42():
     ]
 
 def _seg_43():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0xFA82, 'M', '廒'),
     (0xFA83, 'M', '廙'),
@@ -4581,6 +4627,7 @@ def _seg_43():
     ]
 
 def _seg_44():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0xFB17, 'M', 'մխ'),
     (0xFB18, 'X'),
@@ -4685,6 +4732,7 @@ def _seg_44():
     ]
 
 def _seg_45():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0xFBF4, 'M', 'ئۈ'),
     (0xFBF6, 'M', 'ئې'),
@@ -4789,6 +4837,7 @@ def _seg_45():
     ]
 
 def _seg_46():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0xFC60, '3', ' َّ'),
     (0xFC61, '3', ' ُّ'),
@@ -4893,6 +4942,7 @@ def _seg_46():
     ]
 
 def _seg_47():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0xFCC4, 'M', 'كج'),
     (0xFCC5, 'M', 'كح'),
@@ -4997,6 +5047,7 @@ def _seg_47():
     ]
 
 def _seg_48():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0xFD28, 'M', 'شم'),
     (0xFD29, 'M', 'شر'),
@@ -5101,6 +5152,7 @@ def _seg_48():
     ]
 
 def _seg_49():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0xFDAF, 'M', 'يجي'),
     (0xFDB0, 'M', 'يمي'),
@@ -5205,6 +5257,7 @@ def _seg_49():
     ]
 
 def _seg_50():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0xFE67, 'X'),
     (0xFE68, '3', '\\'),
@@ -5309,6 +5362,7 @@ def _seg_50():
     ]
 
 def _seg_51():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0xFF24, 'M', 'd'),
     (0xFF25, 'M', 'e'),
@@ -5413,6 +5467,7 @@ def _seg_51():
     ]
 
 def _seg_52():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0xFF88, 'M', 'ネ'),
     (0xFF89, 'M', 'ノ'),
@@ -5517,6 +5572,7 @@ def _seg_52():
     ]
 
 def _seg_53():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x10027, 'X'),
     (0x10028, 'V'),
@@ -5621,6 +5677,7 @@ def _seg_53():
     ]
 
 def _seg_54():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x104BF, 'M', '𐓧'),
     (0x104C0, 'M', '𐓨'),
@@ -5725,6 +5782,7 @@ def _seg_54():
     ]
 
 def _seg_55():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x10C00, 'V'),
     (0x10C49, 'X'),
@@ -5829,6 +5887,7 @@ def _seg_55():
     ]
 
 def _seg_56():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x11213, 'V'),
     (0x1123F, 'X'),
@@ -5933,6 +5992,7 @@ def _seg_56():
     ]
 
 def _seg_57():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x118B8, 'M', '𑣘'),
     (0x118B9, 'M', '𑣙'),
@@ -6037,6 +6097,7 @@ def _seg_57():
     ]
 
 def _seg_58():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x16A60, 'V'),
     (0x16A6A, 'X'),
@@ -6141,6 +6202,7 @@ def _seg_58():
     ]
 
 def _seg_59():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x1D173, 'X'),
     (0x1D17B, 'V'),
@@ -6245,6 +6307,7 @@ def _seg_59():
     ]
 
 def _seg_60():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x1D452, 'M', 'e'),
     (0x1D453, 'M', 'f'),
@@ -6349,6 +6412,7 @@ def _seg_60():
     ]
 
 def _seg_61():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x1D4B9, 'M', 'd'),
     (0x1D4BA, 'X'),
@@ -6453,6 +6517,7 @@ def _seg_61():
     ]
 
 def _seg_62():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x1D51E, 'M', 'a'),
     (0x1D51F, 'M', 'b'),
@@ -6557,6 +6622,7 @@ def _seg_62():
     ]
 
 def _seg_63():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x1D584, 'M', 'y'),
     (0x1D585, 'M', 'z'),
@@ -6661,6 +6727,7 @@ def _seg_63():
     ]
 
 def _seg_64():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x1D5E8, 'M', 'u'),
     (0x1D5E9, 'M', 'v'),
@@ -6765,6 +6832,7 @@ def _seg_64():
     ]
 
 def _seg_65():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x1D64C, 'M', 'q'),
     (0x1D64D, 'M', 'r'),
@@ -6869,6 +6937,7 @@ def _seg_65():
     ]
 
 def _seg_66():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x1D6B1, 'M', 'κ'),
     (0x1D6B2, 'M', 'λ'),
@@ -6973,6 +7042,7 @@ def _seg_66():
     ]
 
 def _seg_67():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x1D717, 'M', 'θ'),
     (0x1D718, 'M', 'κ'),
@@ -7077,6 +7147,7 @@ def _seg_67():
     ]
 
 def _seg_68():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x1D77C, 'M', 'ν'),
     (0x1D77D, 'M', 'ξ'),
@@ -7181,6 +7252,7 @@ def _seg_68():
     ]
 
 def _seg_69():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x1D7E4, 'M', '2'),
     (0x1D7E5, 'M', '3'),
@@ -7285,6 +7357,7 @@ def _seg_69():
     ]
 
 def _seg_70():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x1EC71, 'V'),
     (0x1ECB5, 'X'),
@@ -7389,6 +7462,7 @@ def _seg_70():
     ]
 
 def _seg_71():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x1EE6B, 'X'),
     (0x1EE6C, 'M', 'م'),
@@ -7493,6 +7567,7 @@ def _seg_71():
     ]
 
 def _seg_72():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x1F109, '3', '8,'),
     (0x1F10A, '3', '9,'),
@@ -7597,6 +7672,7 @@ def _seg_72():
     ]
 
 def _seg_73():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x1F224, 'M', '声'),
     (0x1F225, 'M', '吹'),
@@ -7701,6 +7777,7 @@ def _seg_73():
     ]
 
 def _seg_74():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x1FBFA, 'X'),
     (0x20000, 'V'),
@@ -7805,6 +7882,7 @@ def _seg_74():
     ]
 
 def _seg_75():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x2F85C, 'M', '夆'),
     (0x2F85D, 'M', '多'),
@@ -7909,6 +7987,7 @@ def _seg_75():
     ]
 
 def _seg_76():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x2F8C3, 'M', '摩'),
     (0x2F8C4, 'M', '摾'),
@@ -8013,6 +8092,7 @@ def _seg_76():
     ]
 
 def _seg_77():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x2F927, 'M', '𤠔'),
     (0x2F928, 'M', '獺'),
@@ -8117,6 +8197,7 @@ def _seg_77():
     ]
 
 def _seg_78():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x2F98E, 'M', '䑫'),
     (0x2F98F, 'M', '芑'),
@@ -8221,6 +8302,7 @@ def _seg_78():
     ]
 
 def _seg_79():
+    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]
     return [
     (0x2F9F2, 'M', '䧦'),
     (0x2F9F3, 'M', '雃'),
@@ -8353,4 +8435,4 @@ def _seg_79():
     + _seg_77()
     + _seg_78()
     + _seg_79()
-)
+)  # type: Tuple[Union[Tuple[int, str], Tuple[int, str, str]], ...]
diff --git a/idna/uts46data.pyi b/idna/uts46data.pyi
deleted file mode 100644
index 5937034..0000000
--- a/idna/uts46data.pyi
+++ /dev/null
@@ -1,4 +0,0 @@
-from typing import Tuple, Union
-
-__version__: str
-uts46data: Tuple[Union[Tuple[int, str], Tuple[int, str, str]], ...]
diff --git a/setup.py b/setup.py
index d4c95ba..3ea5678 100644
--- a/setup.py
+++ b/setup.py
@@ -22,7 +22,7 @@ def main():
     arguments = {
         'name': 'idna',
         'packages': ['idna'],
-        'package_data': {'idna': ['py.typed', '*.pyi']},
+        'package_data': {'idna': ['py.typed']},
         'include_package_data': True,
         'version': package_data['__version__'],
         'description': 'Internationalized Domain Names in Applications (IDNA)',
@@ -51,7 +51,7 @@ def main():
             'Topic :: Software Development :: Libraries :: Python Modules',
             'Topic :: Utilities',
         ],
-        'python_requires': '>=3.4',
+        'python_requires': '>=3.5',
         'test_suite': 'tests',
     }
 
diff --git a/tools/idna-data b/tools/idna-data
index 00c0f4e..dae8901 100755
--- a/tools/idna-data
+++ b/tools/idna-data
@@ -575,6 +575,7 @@ def uts46_libdata(ucdata):
 
     yield '# This file is automatically generated by tools/idna-data'
     yield '# vim: set fileencoding=utf-8 :\n'
+    yield 'from typing import List, Tuple, Union\n\n'
     yield '"""IDNA Mapping Table from UTS46."""\n\n'
 
     yield '__version__ = \'{}\''.format(ucdata.version)
@@ -585,7 +586,7 @@ def uts46_libdata(ucdata):
         if idx % UTS46_SEGMENT_SIZE == 0:
             if idx != 0:
                 yield '    ]\n'
-            yield 'def _seg_{}():\n    return ['.format(idx // UTS46_SEGMENT_SIZE)
+            yield 'def _seg_{}():\n    # type: () -> List[Union[Tuple[int, str], Tuple[int, str, str]]]\n    return ['.format(idx // UTS46_SEGMENT_SIZE)
         yield '    {},'.format(row)
     yield '    ]\n'
 
@@ -593,7 +594,7 @@ def uts46_libdata(ucdata):
     yield '    _seg_0()'
     for i in range(1, idx // UTS46_SEGMENT_SIZE + 1):
         yield '    + _seg_{}()'.format(i)
-    yield ')'
+    yield ')  # type: Tuple[Union[Tuple[int, str], Tuple[int, str, str]], ...]'
 
 def make_libdata(args, ucdata):