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..bcf5986 100644
--- a/idna/codec.py
+++ b/idna/codec.py
@@ -1,3 +1,4 @@
+# type: ignore
 from .core import encode, decode, alabel, ulabel, IDNAError
 import codecs
 import re
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..eadd901 100644
--- a/idna/compat.py
+++ b/idna/compat.py
@@ -1,12 +1,13 @@
 from .core import *
 from .codec import *
+from typing import Any
 
-def ToASCII(label):
+def ToASCII(label: str) -> bytes:
     return encode(label)
 
-def ToUnicode(label):
+def ToUnicode(label: bytes) -> str:
     return decode(label)
 
-def nameprep(s):
+def nameprep(s: 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..bd8c34f 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
@@ -29,38 +29,38 @@ class InvalidCodepointContext(IDNAError):
     pass
 
 
-def _combining_class(cp):
+def _combining_class(cp: int) -> int:
     v = unicodedata.combining(chr(cp))
     if v == 0:
         if not unicodedata.name(chr(cp)):
             raise ValueError('Unknown character in unicodedata')
     return v
 
-def _is_script(cp, script):
+def _is_script(cp: str, script: str) -> bool:
     return intranges_contain(ord(cp), idnadata.scripts[script])
 
-def _punycode(s):
+def _punycode(s: str) -> bytes:
     return s.encode('punycode')
 
-def _unot(s):
+def _unot(s: int) -> str:
     return 'U+{:04X}'.format(s)
 
 
-def valid_label_length(label):
+def valid_label_length(label: Union[bytes, str]) -> bool:
 
     if len(label) > 63:
         return False
     return True
 
 
-def valid_string_length(label, trailing_dot):
+def valid_string_length(label: Union[bytes, str], trailing_dot: bool) -> bool:
 
     if len(label) > (254 if trailing_dot else 253):
         return False
     return True
 
 
-def check_bidi(label, check_ltr=False):
+def check_bidi(label: str, check_ltr: bool = False) -> bool:
 
     # Bidi rules should only be applied if string contains RTL characters
     bidi_label = False
@@ -84,7 +84,7 @@ 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: Union[str, bool] = False
     for (idx, cp) in enumerate(label, 1):
         direction = unicodedata.bidirectional(cp)
 
@@ -120,14 +120,14 @@ def check_bidi(label, check_ltr=False):
     return True
 
 
-def check_initial_combiner(label):
+def check_initial_combiner(label: 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):
+def check_hyphen_ok(label: str) -> bool:
 
     if label[2:4] == '--':
         raise IDNAError('Label has disallowed hyphens in 3rd and 4th position')
@@ -136,13 +136,13 @@ def check_hyphen_ok(label):
     return True
 
 
-def check_nfc(label):
+def check_nfc(label: str) -> None:
 
     if unicodedata.normalize('NFC', label) != label:
         raise IDNAError('Label must be in Normalization Form C')
 
 
-def valid_contextj(label, pos):
+def valid_contextj(label: str, pos: int) -> bool:
 
     cp_value = ord(label[pos])
 
@@ -186,7 +186,7 @@ def valid_contextj(label, pos):
         return False
 
 
-def valid_contexto(label, pos, exception=False):
+def valid_contexto(label: str, pos: int, exception: bool = False) -> bool:
 
     cp_value = ord(label[pos])
 
@@ -226,8 +226,10 @@ def valid_contexto(label, pos, exception=False):
                 return False
         return True
 
+    return False
 
-def check_label(label):
+
+def check_label(label: Union[str, bytes, bytearray]) -> None:
 
     if isinstance(label, (bytes, bytearray)):
         label = label.decode('utf-8')
@@ -259,14 +261,14 @@ def check_label(label):
     check_bidi(label)
 
 
-def alabel(label):
+def alabel(label: 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 +277,58 @@ 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):
+def ulabel(label: 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):
+def uts46_remap(domain: str, std3_rules: bool = True, transitional: bool = False) -> 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: Optional[str]
+            if len(uts46row) == 3:
+                replacement = uts46row[2]  # type: ignore
+            else:
+                replacement = None
             if (status == 'V' or
                     (status == 'D' and not transitional) or
                     (status == '3' and not std3_rules and replacement is None)):
@@ -330,14 +339,19 @@ 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: Union[str, bytes, bytearray],
+           strict: bool = False,
+           uts46: bool = False,
+           std3_rules: bool = False,
+           transitional: bool = False) -> bytes:
 
     if isinstance(s, (bytes, bytearray)):
         s = s.decode('ascii')
@@ -368,7 +382,10 @@ def encode(s, strict=False, uts46=False, std3_rules=False, transitional=False):
     return s
 
 
-def decode(s, strict=False, uts46=False, std3_rules=False):
+def decode(s: Union[str, bytes, bytearray],
+           strict: bool = False,
+           uts46: bool = False,
+           std3_rules: bool = False) -> str:
 
     if isinstance(s, (bytes, bytearray)):
         s = s.decode('ascii')
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..6a43b04 100644
--- a/idna/intranges.py
+++ b/idna/intranges.py
@@ -6,8 +6,9 @@
 """
 
 import bisect
+from typing import List, Tuple
 
-def intranges_from_list(list_):
+def intranges_from_list(list_: 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.
@@ -28,14 +29,14 @@ def intranges_from_list(list_):
 
     return tuple(ranges)
 
-def _encode_range(start, end):
+def _encode_range(start: int, end: int) -> int:
     return (start << 32) | end
 
-def _decode_range(r):
+def _decode_range(r: int) -> Tuple[int, int]:
     return (r >> 32), (r & ((1 << 32) - 1))
 
 
-def intranges_contain(int_, ranges):
+def intranges_contain(int_: int, ranges: 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..2f56cd1 100644
--- a/idna/uts46data.py
+++ b/idna/uts46data.py
@@ -1,10 +1,12 @@
 # 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():
+def _seg_0() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x0, '3'),
     (0x1, '3'),
@@ -108,7 +110,7 @@ def _seg_0():
     (0x63, 'V'),
     ]
 
-def _seg_1():
+def _seg_1() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x64, 'V'),
     (0x65, 'V'),
@@ -212,7 +214,7 @@ def _seg_1():
     (0xC7, 'M', 'ç'),
     ]
 
-def _seg_2():
+def _seg_2() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0xC8, 'M', 'è'),
     (0xC9, 'M', 'é'),
@@ -316,7 +318,7 @@ def _seg_2():
     (0x12B, 'V'),
     ]
 
-def _seg_3():
+def _seg_3() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x12C, 'M', 'ĭ'),
     (0x12D, 'V'),
@@ -420,7 +422,7 @@ def _seg_3():
     (0x193, 'M', 'ɠ'),
     ]
 
-def _seg_4():
+def _seg_4() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x194, 'M', 'ɣ'),
     (0x195, 'V'),
@@ -524,7 +526,7 @@ def _seg_4():
     (0x20C, 'M', 'ȍ'),
     ]
 
-def _seg_5():
+def _seg_5() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x20D, 'V'),
     (0x20E, 'M', 'ȏ'),
@@ -628,7 +630,7 @@ def _seg_5():
     (0x377, 'V'),
     ]
 
-def _seg_6():
+def _seg_6() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x378, 'X'),
     (0x37A, '3', ' ι'),
@@ -732,7 +734,7 @@ def _seg_6():
     (0x402, 'M', 'ђ'),
     ]
 
-def _seg_7():
+def _seg_7() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x403, 'M', 'ѓ'),
     (0x404, 'M', 'є'),
@@ -836,7 +838,7 @@ def _seg_7():
     (0x49D, 'V'),
     ]
 
-def _seg_8():
+def _seg_8() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x49E, 'M', 'ҟ'),
     (0x49F, 'V'),
@@ -940,7 +942,7 @@ def _seg_8():
     (0x502, 'M', 'ԃ'),
     ]
 
-def _seg_9():
+def _seg_9() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x503, 'V'),
     (0x504, 'M', 'ԅ'),
@@ -1044,7 +1046,7 @@ def _seg_9():
     (0x61E, 'V'),
     ]
 
-def _seg_10():
+def _seg_10() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x675, 'M', 'اٴ'),
     (0x676, 'M', 'وٴ'),
@@ -1148,7 +1150,7 @@ def _seg_10():
     (0xA5B, 'M', 'ਜ਼'),
     ]
 
-def _seg_11():
+def _seg_11() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0xA5C, 'V'),
     (0xA5D, 'X'),
@@ -1252,7 +1254,7 @@ def _seg_11():
     (0xC12, 'V'),
     ]
 
-def _seg_12():
+def _seg_12() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0xC29, 'X'),
     (0xC2A, 'V'),
@@ -1356,7 +1358,7 @@ def _seg_12():
     (0xEB4, 'V'),
     ]
 
-def _seg_13():
+def _seg_13() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0xEBE, 'X'),
     (0xEC0, 'V'),
@@ -1460,7 +1462,7 @@ def _seg_13():
     (0x1312, 'V'),
     ]
 
-def _seg_14():
+def _seg_14() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x1316, 'X'),
     (0x1318, 'V'),
@@ -1564,7 +1566,7 @@ def _seg_14():
     (0x1C4D, 'V'),
     ]
 
-def _seg_15():
+def _seg_15() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x1C80, 'M', 'в'),
     (0x1C81, 'M', 'д'),
@@ -1668,7 +1670,7 @@ def _seg_15():
     (0x1D52, 'M', 'o'),
     ]
 
-def _seg_16():
+def _seg_16() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x1D53, 'M', 'ɔ'),
     (0x1D54, 'M', 'ᴖ'),
@@ -1772,7 +1774,7 @@ def _seg_16():
     (0x1E20, 'M', 'ḡ'),
     ]
 
-def _seg_17():
+def _seg_17() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x1E21, 'V'),
     (0x1E22, 'M', 'ḣ'),
@@ -1876,7 +1878,7 @@ def _seg_17():
     (0x1E84, 'M', 'ẅ'),
     ]
 
-def _seg_18():
+def _seg_18() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x1E85, 'V'),
     (0x1E86, 'M', 'ẇ'),
@@ -1980,7 +1982,7 @@ def _seg_18():
     (0x1EED, 'V'),
     ]
 
-def _seg_19():
+def _seg_19() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x1EEE, 'M', 'ữ'),
     (0x1EEF, 'V'),
@@ -2084,7 +2086,7 @@ def _seg_19():
     (0x1F84, 'M', 'ἄι'),
     ]
 
-def _seg_20():
+def _seg_20() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x1F85, 'M', 'ἅι'),
     (0x1F86, 'M', 'ἆι'),
@@ -2188,7 +2190,7 @@ def _seg_20():
     (0x1FF3, 'M', 'ωι'),
     ]
 
-def _seg_21():
+def _seg_21() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x1FF4, 'M', 'ώι'),
     (0x1FF5, 'X'),
@@ -2292,7 +2294,7 @@ def _seg_21():
     (0x2101, '3', 'a/s'),
     ]
 
-def _seg_22():
+def _seg_22() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x2102, 'M', 'c'),
     (0x2103, 'M', '°c'),
@@ -2396,7 +2398,7 @@ def _seg_22():
     (0x2179, 'M', 'x'),
     ]
 
-def _seg_23():
+def _seg_23() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x217A, 'M', 'xi'),
     (0x217B, 'M', 'xii'),
@@ -2500,7 +2502,7 @@ def _seg_23():
     (0x24B9, 'M', 'd'),
     ]
 
-def _seg_24():
+def _seg_24() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x24BA, 'M', 'e'),
     (0x24BB, 'M', 'f'),
@@ -2604,7 +2606,7 @@ def _seg_24():
     (0x2C25, 'M', 'ⱕ'),
     ]
 
-def _seg_25():
+def _seg_25() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x2C26, 'M', 'ⱖ'),
     (0x2C27, 'M', 'ⱗ'),
@@ -2708,7 +2710,7 @@ def _seg_25():
     (0x2CBE, 'M', 'ⲿ'),
     ]
 
-def _seg_26():
+def _seg_26() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x2CBF, 'V'),
     (0x2CC0, 'M', 'ⳁ'),
@@ -2812,7 +2814,7 @@ def _seg_26():
     (0x2F11, 'M', '刀'),
     ]
 
-def _seg_27():
+def _seg_27() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x2F12, 'M', '力'),
     (0x2F13, 'M', '勹'),
@@ -2916,7 +2918,7 @@ def _seg_27():
     (0x2F75, 'M', '竹'),
     ]
 
-def _seg_28():
+def _seg_28() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x2F76, 'M', '米'),
     (0x2F77, 'M', '糸'),
@@ -3020,7 +3022,7 @@ def _seg_28():
     (0x3002, 'M', '.'),
     ]
 
-def _seg_29():
+def _seg_29() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x3003, 'V'),
     (0x3036, 'M', '〒'),
@@ -3124,7 +3126,7 @@ def _seg_29():
     (0x3180, 'M', 'ᅇ'),
     ]
 
-def _seg_30():
+def _seg_30() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x3181, 'M', 'ᅌ'),
     (0x3182, 'M', 'ᇱ'),
@@ -3228,7 +3230,7 @@ def _seg_30():
     (0x3242, '3', '(自)'),
     ]
 
-def _seg_31():
+def _seg_31() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x3243, '3', '(至)'),
     (0x3244, 'M', '問'),
@@ -3332,7 +3334,7 @@ def _seg_31():
     (0x32AD, 'M', '企'),
     ]
 
-def _seg_32():
+def _seg_32() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x32AE, 'M', '資'),
     (0x32AF, 'M', '協'),
@@ -3436,7 +3438,7 @@ def _seg_32():
     (0x3311, 'M', 'ギニー'),
     ]
 
-def _seg_33():
+def _seg_33() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x3312, 'M', 'キュリー'),
     (0x3313, 'M', 'ギルダー'),
@@ -3540,7 +3542,7 @@ def _seg_33():
     (0x3375, 'M', 'ov'),
     ]
 
-def _seg_34():
+def _seg_34() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x3376, 'M', 'pc'),
     (0x3377, 'M', 'dm'),
@@ -3644,7 +3646,7 @@ def _seg_34():
     (0x33D9, 'M', 'ppm'),
     ]
 
-def _seg_35():
+def _seg_35() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x33DA, 'M', 'pr'),
     (0x33DB, 'M', 'sr'),
@@ -3748,7 +3750,7 @@ def _seg_35():
     (0xA687, 'V'),
     ]
 
-def _seg_36():
+def _seg_36() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0xA688, 'M', 'ꚉ'),
     (0xA689, 'V'),
@@ -3852,7 +3854,7 @@ def _seg_36():
     (0xA76E, 'M', 'ꝯ'),
     ]
 
-def _seg_37():
+def _seg_37() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0xA76F, 'V'),
     (0xA770, 'M', 'ꝯ'),
@@ -3956,7 +3958,7 @@ def _seg_37():
     (0xA9CF, 'V'),
     ]
 
-def _seg_38():
+def _seg_38() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0xA9DA, 'X'),
     (0xA9DE, 'V'),
@@ -4060,7 +4062,7 @@ def _seg_38():
     (0xABB3, 'M', 'Ꮳ'),
     ]
 
-def _seg_39():
+def _seg_39() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0xABB4, 'M', 'Ꮴ'),
     (0xABB5, 'M', 'Ꮵ'),
@@ -4164,7 +4166,7 @@ def _seg_39():
     (0xF94E, 'M', '漏'),
     ]
 
-def _seg_40():
+def _seg_40() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0xF94F, 'M', '累'),
     (0xF950, 'M', '縷'),
@@ -4268,7 +4270,7 @@ def _seg_40():
     (0xF9B2, 'M', '零'),
     ]
 
-def _seg_41():
+def _seg_41() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0xF9B3, 'M', '靈'),
     (0xF9B4, 'M', '領'),
@@ -4372,7 +4374,7 @@ def _seg_41():
     (0xFA18, 'M', '礼'),
     ]
 
-def _seg_42():
+def _seg_42() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0xFA19, 'M', '神'),
     (0xFA1A, 'M', '祥'),
@@ -4476,7 +4478,7 @@ def _seg_42():
     (0xFA81, 'M', '嬨'),
     ]
 
-def _seg_43():
+def _seg_43() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0xFA82, 'M', '廒'),
     (0xFA83, 'M', '廙'),
@@ -4580,7 +4582,7 @@ def _seg_43():
     (0xFB16, 'M', 'վն'),
     ]
 
-def _seg_44():
+def _seg_44() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0xFB17, 'M', 'մխ'),
     (0xFB18, 'X'),
@@ -4684,7 +4686,7 @@ def _seg_44():
     (0xFBF2, 'M', 'ئۆ'),
     ]
 
-def _seg_45():
+def _seg_45() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0xFBF4, 'M', 'ئۈ'),
     (0xFBF6, 'M', 'ئې'),
@@ -4788,7 +4790,7 @@ def _seg_45():
     (0xFC5F, '3', ' ٍّ'),
     ]
 
-def _seg_46():
+def _seg_46() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0xFC60, '3', ' َّ'),
     (0xFC61, '3', ' ُّ'),
@@ -4892,7 +4894,7 @@ def _seg_46():
     (0xFCC3, 'M', 'قم'),
     ]
 
-def _seg_47():
+def _seg_47() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0xFCC4, 'M', 'كج'),
     (0xFCC5, 'M', 'كح'),
@@ -4996,7 +4998,7 @@ def _seg_47():
     (0xFD27, 'M', 'شخ'),
     ]
 
-def _seg_48():
+def _seg_48() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0xFD28, 'M', 'شم'),
     (0xFD29, 'M', 'شر'),
@@ -5100,7 +5102,7 @@ def _seg_48():
     (0xFDAE, 'M', 'يحي'),
     ]
 
-def _seg_49():
+def _seg_49() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0xFDAF, 'M', 'يجي'),
     (0xFDB0, 'M', 'يمي'),
@@ -5204,7 +5206,7 @@ def _seg_49():
     (0xFE66, '3', '='),
     ]
 
-def _seg_50():
+def _seg_50() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0xFE67, 'X'),
     (0xFE68, '3', '\\'),
@@ -5308,7 +5310,7 @@ def _seg_50():
     (0xFF23, 'M', 'c'),
     ]
 
-def _seg_51():
+def _seg_51() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0xFF24, 'M', 'd'),
     (0xFF25, 'M', 'e'),
@@ -5412,7 +5414,7 @@ def _seg_51():
     (0xFF87, 'M', 'ヌ'),
     ]
 
-def _seg_52():
+def _seg_52() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0xFF88, 'M', 'ネ'),
     (0xFF89, 'M', 'ノ'),
@@ -5516,7 +5518,7 @@ def _seg_52():
     (0x1000D, 'V'),
     ]
 
-def _seg_53():
+def _seg_53() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x10027, 'X'),
     (0x10028, 'V'),
@@ -5620,7 +5622,7 @@ def _seg_53():
     (0x104BE, 'M', '𐓦'),
     ]
 
-def _seg_54():
+def _seg_54() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x104BF, 'M', '𐓧'),
     (0x104C0, 'M', '𐓨'),
@@ -5724,7 +5726,7 @@ def _seg_54():
     (0x10BB0, 'X'),
     ]
 
-def _seg_55():
+def _seg_55() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x10C00, 'V'),
     (0x10C49, 'X'),
@@ -5828,7 +5830,7 @@ def _seg_55():
     (0x11212, 'X'),
     ]
 
-def _seg_56():
+def _seg_56() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x11213, 'V'),
     (0x1123F, 'X'),
@@ -5932,7 +5934,7 @@ def _seg_56():
     (0x118B7, 'M', '𑣗'),
     ]
 
-def _seg_57():
+def _seg_57() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x118B8, 'M', '𑣘'),
     (0x118B9, 'M', '𑣙'),
@@ -6036,7 +6038,7 @@ def _seg_57():
     (0x16A5F, 'X'),
     ]
 
-def _seg_58():
+def _seg_58() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x16A60, 'V'),
     (0x16A6A, 'X'),
@@ -6140,7 +6142,7 @@ def _seg_58():
     (0x1D165, 'V'),
     ]
 
-def _seg_59():
+def _seg_59() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x1D173, 'X'),
     (0x1D17B, 'V'),
@@ -6244,7 +6246,7 @@ def _seg_59():
     (0x1D451, 'M', 'd'),
     ]
 
-def _seg_60():
+def _seg_60() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x1D452, 'M', 'e'),
     (0x1D453, 'M', 'f'),
@@ -6348,7 +6350,7 @@ def _seg_60():
     (0x1D4B8, 'M', 'c'),
     ]
 
-def _seg_61():
+def _seg_61() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x1D4B9, 'M', 'd'),
     (0x1D4BA, 'X'),
@@ -6452,7 +6454,7 @@ def _seg_61():
     (0x1D51D, 'X'),
     ]
 
-def _seg_62():
+def _seg_62() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x1D51E, 'M', 'a'),
     (0x1D51F, 'M', 'b'),
@@ -6556,7 +6558,7 @@ def _seg_62():
     (0x1D583, 'M', 'x'),
     ]
 
-def _seg_63():
+def _seg_63() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x1D584, 'M', 'y'),
     (0x1D585, 'M', 'z'),
@@ -6660,7 +6662,7 @@ def _seg_63():
     (0x1D5E7, 'M', 't'),
     ]
 
-def _seg_64():
+def _seg_64() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x1D5E8, 'M', 'u'),
     (0x1D5E9, 'M', 'v'),
@@ -6764,7 +6766,7 @@ def _seg_64():
     (0x1D64B, 'M', 'p'),
     ]
 
-def _seg_65():
+def _seg_65() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x1D64C, 'M', 'q'),
     (0x1D64D, 'M', 'r'),
@@ -6868,7 +6870,7 @@ def _seg_65():
     (0x1D6B0, 'M', 'ι'),
     ]
 
-def _seg_66():
+def _seg_66() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x1D6B1, 'M', 'κ'),
     (0x1D6B2, 'M', 'λ'),
@@ -6972,7 +6974,7 @@ def _seg_66():
     (0x1D716, 'M', 'ε'),
     ]
 
-def _seg_67():
+def _seg_67() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x1D717, 'M', 'θ'),
     (0x1D718, 'M', 'κ'),
@@ -7076,7 +7078,7 @@ def _seg_67():
     (0x1D77B, 'M', 'μ'),
     ]
 
-def _seg_68():
+def _seg_68() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x1D77C, 'M', 'ν'),
     (0x1D77D, 'M', 'ξ'),
@@ -7180,7 +7182,7 @@ def _seg_68():
     (0x1D7E3, 'M', '1'),
     ]
 
-def _seg_69():
+def _seg_69() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x1D7E4, 'M', '2'),
     (0x1D7E5, 'M', '3'),
@@ -7284,7 +7286,7 @@ def _seg_69():
     (0x1E960, 'X'),
     ]
 
-def _seg_70():
+def _seg_70() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x1EC71, 'V'),
     (0x1ECB5, 'X'),
@@ -7388,7 +7390,7 @@ def _seg_70():
     (0x1EE6A, 'M', 'ك'),
     ]
 
-def _seg_71():
+def _seg_71() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x1EE6B, 'X'),
     (0x1EE6C, 'M', 'م'),
@@ -7492,7 +7494,7 @@ def _seg_71():
     (0x1F108, '3', '7,'),
     ]
 
-def _seg_72():
+def _seg_72() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x1F109, '3', '8,'),
     (0x1F10A, '3', '9,'),
@@ -7596,7 +7598,7 @@ def _seg_72():
     (0x1F223, 'M', '販'),
     ]
 
-def _seg_73():
+def _seg_73() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x1F224, 'M', '声'),
     (0x1F225, 'M', '吹'),
@@ -7700,7 +7702,7 @@ def _seg_73():
     (0x1FBF9, 'M', '9'),
     ]
 
-def _seg_74():
+def _seg_74() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x1FBFA, 'X'),
     (0x20000, 'V'),
@@ -7804,7 +7806,7 @@ def _seg_74():
     (0x2F85B, 'M', '壷'),
     ]
 
-def _seg_75():
+def _seg_75() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x2F85C, 'M', '夆'),
     (0x2F85D, 'M', '多'),
@@ -7908,7 +7910,7 @@ def _seg_75():
     (0x2F8C2, 'M', '㨮'),
     ]
 
-def _seg_76():
+def _seg_76() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x2F8C3, 'M', '摩'),
     (0x2F8C4, 'M', '摾'),
@@ -8012,7 +8014,7 @@ def _seg_76():
     (0x2F926, 'M', '𤜵'),
     ]
 
-def _seg_77():
+def _seg_77() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x2F927, 'M', '𤠔'),
     (0x2F928, 'M', '獺'),
@@ -8116,7 +8118,7 @@ def _seg_77():
     (0x2F98D, 'M', '辞'),
     ]
 
-def _seg_78():
+def _seg_78() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x2F98E, 'M', '䑫'),
     (0x2F98F, 'M', '芑'),
@@ -8220,7 +8222,7 @@ def _seg_78():
     (0x2F9F1, 'M', '𨵷'),
     ]
 
-def _seg_79():
+def _seg_79() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:
     return [
     (0x2F9F2, 'M', '䧦'),
     (0x2F9F3, 'M', '雃'),
@@ -8272,7 +8274,7 @@ def _seg_79():
     (0xE01F0, 'X'),
     ]
 
-uts46data = tuple(
+uts46data: Tuple[Union[Tuple[int, str], Tuple[int, str, str]], ...] = tuple(
     _seg_0()
     + _seg_1()
     + _seg_2()
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..8a7847b 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)
@@ -585,11 +586,11 @@ 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_{}() -> List[Union[Tuple[int, str], Tuple[int, str, str]]]:\n    return ['.format(idx // UTS46_SEGMENT_SIZE)
         yield '    {},'.format(row)
     yield '    ]\n'
 
-    yield 'uts46data = tuple('
+    yield 'uts46data: Tuple[Union[Tuple[int, str], Tuple[int, str, str]], ...] = tuple('
     yield '    _seg_0()'
     for i in range(1, idx // UTS46_SEGMENT_SIZE + 1):
         yield '    + _seg_{}()'.format(i)