diff --git a/src/docformatter/classify.py b/src/docformatter/classify.py
index 9b8b553..f0db043 100644
--- a/src/docformatter/classify.py
+++ b/src/docformatter/classify.py
@@ -446,7 +446,7 @@ def is_nested_definition_line(token: tokenize.TokenInfo) -> bool:
     bool
         True if the token is a nested definition line, False otherwise.
     """
-    return re.match(r"^ {4,}(async|class|def) ", token.line) is not None
+    return re.match(r"^ {4,}(?:async def|class|def) ", token.line) is not None
 
 
 def is_newline_continuation(
diff --git a/tests/_data/string_files/classify_functions.toml b/tests/_data/string_files/classify_functions.toml
index fc40460..6ef9726 100644
--- a/tests/_data/string_files/classify_functions.toml
+++ b/tests/_data/string_files/classify_functions.toml
@@ -122,6 +122,14 @@ end = "(3,25)"
 line = '    async def foo():\n'
 expected = true
 
+[is_not_nested_definition_line_async_with]
+type = 1
+string = '    async with lock:\n'
+start = "(3,10)"
+end = "(3,30)"
+line = '    async with lock:\n'
+expected = false
+
 [is_not_nested_definition_line_function]
 type = 1
 string = '    definitely\n'
diff --git a/tests/_data/string_files/do_format_code.toml b/tests/_data/string_files/do_format_code.toml
index d652a15..64c9291 100644
--- a/tests/_data/string_files/do_format_code.toml
+++ b/tests/_data/string_files/do_format_code.toml
@@ -1245,6 +1245,18 @@ expected='''"""A."""
 pass
 '''
 
+[issue_351]
+source='''async def example() -> None:
+    """Example."""
+    async with lock:
+        pass
+'''
+expected='''async def example() -> None:
+    """Example."""
+    async with lock:
+        pass
+'''
+
 # A blank line with trailing whitespace must not crash the tokenizer round-trip.
 # The "\n" escapes are used so the four trailing spaces on the blank line are
 # explicit and cannot be stripped by editors or formatters.
diff --git a/tests/formatter/test_do_format_code.py b/tests/formatter/test_do_format_code.py
index 037ace1..4cd7a71 100644
--- a/tests/formatter/test_do_format_code.py
+++ b/tests/formatter/test_do_format_code.py
@@ -141,6 +141,7 @@
         ("do_not_break_f_string_double_quotes", NO_ARGS),
         ("do_not_break_f_string_single_quotes", NO_ARGS),
         ("issue_331_black_module_docstring", ["--black", ""]),
+        ("issue_351", NO_ARGS),
         ("issue_355", NO_ARGS),
         ("issue_360_no_trailing_newline", NO_ARGS),
     ],
diff --git a/tests/test_classify_functions.py b/tests/test_classify_functions.py
index d959bc2..55f8e6e 100644
--- a/tests/test_classify_functions.py
+++ b/tests/test_classify_functions.py
@@ -144,6 +144,7 @@ def test_is_not_attribute_docstring_inside_brackets(source):
         ("is_nested_definition_line_class", is_nested_definition_line),
         ("is_nested_definition_line_function", is_nested_definition_line),
         ("is_nested_definition_line_async_function", is_nested_definition_line),
+        ("is_not_nested_definition_line_async_with", is_nested_definition_line),
         ("is_not_nested_definition_line_function", is_nested_definition_line),
         ("is_newline_continuation", is_newline_continuation),
         ("is_string_variable", is_string_variable),