diff --git a/Lib/test/test_type_comments.py b/Lib/test/test_type_comments.py
index dd2e67841651d9..d827ac271085bd 100644
--- a/Lib/test/test_type_comments.py
+++ b/Lib/test/test_type_comments.py
@@ -398,6 +398,9 @@ def test_non_utf8_type_comment_with_ignore_cookie(self):
         with self.assertRaises(UnicodeDecodeError):
             _testcapi.Py_CompileStringExFlags(
                 b"a=1 # type: \x80", "<test>", 256, flags)
+        with self.assertRaises(UnicodeDecodeError):
+            _testcapi.Py_CompileStringExFlags(
+                b"def a(f=8, #type: \x80\n\x80", "<test>", 256, flags)
 
     def test_func_type_input(self):
 
diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2026-04-06-11-15-46.gh-issue-148157.JFnZDn.rst b/Misc/NEWS.d/next/Core_and_Builtins/2026-04-06-11-15-46.gh-issue-148157.JFnZDn.rst
new file mode 100644
index 00000000000000..6565291eb998ed
--- /dev/null
+++ b/Misc/NEWS.d/next/Core_and_Builtins/2026-04-06-11-15-46.gh-issue-148157.JFnZDn.rst
@@ -0,0 +1,2 @@
+Fix an unlikely crash when parsing an invalid type comments for function
+parameters. Found by OSS Fuzz in :oss-fuzz:`492782951`.
diff --git a/Parser/action_helpers.c b/Parser/action_helpers.c
index 57e46b4399c66d..a24744d77eabb9 100644
--- a/Parser/action_helpers.c
+++ b/Parser/action_helpers.c
@@ -435,6 +435,9 @@ _PyPegen_name_default_pair(Parser *p, arg_ty arg, expr_ty value, Token *tc)
         return NULL;
     }
     a->arg = _PyPegen_add_type_comment_to_arg(p, arg, tc);
+    if (!a->arg) {
+        return NULL;
+    }
     a->value = value;
     return a;
 }