diff --git a/test/test_api/test_call_signatures.py b/test/test_api/test_call_signatures.py
index 1789fb1e..ba33b94b 100644
--- a/test/test_api/test_call_signatures.py
+++ b/test/test_api/test_call_signatures.py
@@ -3,6 +3,7 @@ import inspect
 
 from ..helpers import TestCase
 from jedi import Script
+from jedi import cache
 from jedi._compatibility import is_py33
 
 
@@ -224,3 +225,15 @@ def test_no_signature():
     X()(""")
     assert Script(s).call_signatures() == []
     assert len(Script(s, column=2).call_signatures()) == 1
+
+
+def test_completion_interference():
+    """Seems to cause problems, see also #396."""
+    cache.parser_cache.pop(None, None)
+    assert Script('open(').call_signatures()
+    assert Script('open(').call_signatures()
+
+    # complete something usual, before doing the same call_signatures again.
+    assert Script('from os import ').completions()
+
+    assert Script('open(').call_signatures()