diff --git a/src/black/__init__.py b/src/black/__init__.py
index 06295c412e4..ad4ee1a0d1a 100644
--- a/src/black/__init__.py
+++ b/src/black/__init__.py
@@ -1135,9 +1135,14 @@ def get_features_used(node: Node) -> Set[Feature]:  # noqa: C901
             assert isinstance(n, Leaf)
             if "_" in n.value:
                 features.add(Feature.NUMERIC_UNDERSCORES)
-            elif n.value.endswith("L"):
+            elif n.value.endswith(("L", "l")):
                 # Python 2: 10L
                 features.add(Feature.LONG_INT_LITERAL)
+            elif len(n.value) >= 2 and n.value[0] == "0" and n.value[1].isdigit():
+                # Python 2: 0123; 00123; ...
+                if not all(char == "0" for char in n.value):
+                    # although we don't want to match 0000 or similar
+                    features.add(Feature.OCTAL_INT_LITERAL)
 
         elif n.type == token.SLASH:
             if n.parent and n.parent.type in {
@@ -1175,7 +1180,7 @@ def get_features_used(node: Node) -> Set[Feature]:  # noqa: C901
                         if argch.type in STARS:
                             features.add(feature)
 
-        # Python 2 only features (for its deprecation) except for 10L, see above
+        # Python 2 only features (for its deprecation) except for integers, see above
         elif n.type == syms.print_stmt:
             features.add(Feature.PRINT_STMT)
         elif n.type == syms.exec_stmt:
diff --git a/src/black/mode.py b/src/black/mode.py
index 5fd179f4726..01ee336366c 100644
--- a/src/black/mode.py
+++ b/src/black/mode.py
@@ -48,7 +48,8 @@ class Feature(Enum):
     COMMA_STYLE_EXCEPT = 203
     COMMA_STYLE_RAISE = 204
     LONG_INT_LITERAL = 205
-    BACKQUOTE_REPR = 206
+    OCTAL_INT_LITERAL = 206
+    BACKQUOTE_REPR = 207
 
 
 VERSION_TO_FEATURES: Dict[TargetVersion, Set[Feature]] = {
@@ -60,6 +61,7 @@ class Feature(Enum):
         Feature.COMMA_STYLE_EXCEPT,
         Feature.COMMA_STYLE_RAISE,
         Feature.LONG_INT_LITERAL,
+        Feature.OCTAL_INT_LITERAL,
         Feature.BACKQUOTE_REPR,
     },
     TargetVersion.PY33: {Feature.UNICODE_LITERALS, Feature.ASYNC_IDENTIFIERS},
diff --git a/tests/data/python2_detection.py b/tests/data/python2_detection.py
index b75f62fe10a..8de2bb58adc 100644
--- a/tests/data/python2_detection.py
+++ b/tests/data/python2_detection.py
@@ -30,6 +30,14 @@ def set_position((x, y), value):
 
 10L
 
+###
+
+10l
+
+###
+
+0123
+
 # output
 
 print("hello python three!")
@@ -58,9 +66,25 @@ def set_position((x, y), value):
 
 ###
 
+raise RuntimeError("boom!",)
+
+###
+
 def set_position(x, y, value):
     pass
 
 ###
 
 10
+
+###
+
+0
+
+###
+
+000
+
+###
+
+0o12
\ No newline at end of file
diff --git a/tests/test_black.py b/tests/test_black.py
index 7f8fff3cabc..7dbc3809d26 100644
--- a/tests/test_black.py
+++ b/tests/test_black.py
@@ -2039,10 +2039,12 @@ def test_python_2_deprecation_autodetection_extended() -> None:
     python2, non_python2 = read_data("python2_detection")
     for python2_case in python2.split("###"):
         node = black.lib2to3_parse(python2_case)
-        assert black.detect_target_versions(node) == {TargetVersion.PY27}
+        assert black.detect_target_versions(node) == {TargetVersion.PY27}, python2_case
     for non_python2_case in non_python2.split("###"):
         node = black.lib2to3_parse(non_python2_case)
-        assert black.detect_target_versions(node) != {TargetVersion.PY27}
+        assert black.detect_target_versions(node) != {
+            TargetVersion.PY27
+        }, non_python2_case
 
 
 with open(black.__file__, "r", encoding="utf-8") as _bf: