diff --git a/onlinejudge_verify/languages/python.py b/onlinejudge_verify/languages/python.py
index d31d2f54..cd3c1a25 100644
--- a/onlinejudge_verify/languages/python.py
+++ b/onlinejudge_verify/languages/python.py
@@ -57,7 +57,7 @@ def _python_list_depending_files(path: pathlib.Path, basedir: pathlib.Path) -> L
     )
     try:
         executor = concurrent.futures.ThreadPoolExecutor()
-        future = executor.submit(importlab.graph.ImportGraph.create, env, [str(path)])
+        future = executor.submit(importlab.graph.ImportGraph.create, env, [str(path)], trim=True)
         if platform.uname().system == 'Windows':
             timeout = 5.0  # 1.0 sec causes timeout on CI using Windows
         else:
diff --git a/tests/test_python.py b/tests/test_python.py
index 8485edde..8b07b2ae 100644
--- a/tests/test_python.py
+++ b/tests/test_python.py
@@ -66,6 +66,20 @@ def main() -> None:
         main()
 """
 
+TESTS_MAIN_PY_WITH_STDLIB = rb"""\
+# verify-helper: PROBLEM http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=ITP1_1_B
+from library.imported import solve
+import os
+
+def main() -> None:
+    x = int(input())
+    ans = solve(x)
+    print(ans)
+
+if __name__ == "__main__":
+        main()
+"""
+
 
 class TestPythonVerification(unittest.TestCase):
     """TestPythonListDependencies has end-to-end tests for the verification of Python files.
@@ -88,3 +102,23 @@ def test_separated_dir(self) -> None:
                 with open(timestamps_path) as fh:
                     timestamps = json.load(fh)
                 self.assertEqual(list(timestamps.keys()), [str(pathlib.Path('tests', 'main.py'))])
+
+    def test_separated_dir_with_stdlib(self) -> None:
+        """`test_separated_dir_with_stdlib` is a test for the case when the library files exist at the separate directory of the test file.
+        In this test, main.py has an import of a module in stdlib.
+        """
+
+        files = {
+            pathlib.Path('library', '__init__.py'): b"",
+            pathlib.Path('library', 'imported.py'): LIBRARY_IMPORTED_PY,
+            pathlib.Path('tests', 'main.py'): TESTS_MAIN_PY_WITH_STDLIB,
+        }
+        path = pathlib.Path('tests', 'main.py')
+        with tests.utils.load_files_pathlib(files) as tempdir:
+            with tests.utils.chdir(tempdir):
+                timestamps_path = tempdir / 'timestamps.json'
+                with onlinejudge_verify.marker.VerificationMarker(json_path=timestamps_path, use_git_timestamp=False) as marker:
+                    self.assertEqual(verify.main([path], marker=marker).failed_test_paths, [])
+                with open(timestamps_path) as fh:
+                    timestamps = json.load(fh)
+                self.assertEqual(list(timestamps.keys()), [str(pathlib.Path('tests', 'main.py'))])