diff --git a/jedi/evaluate/gradual/conversion.py b/jedi/evaluate/gradual/conversion.py
index 8b56354d..88f49428 100644
--- a/jedi/evaluate/gradual/conversion.py
+++ b/jedi/evaluate/gradual/conversion.py
@@ -41,8 +41,7 @@ def _stub_to_python_context_set(stub_context, ignore_compiled=False):
 
 def _infer_from_stub(stub_module, qualified_names, ignore_compiled):
     from jedi.evaluate.compiled.mixed import MixedObject
-    assert isinstance(stub_module, StubModuleContext) or \
-           isinstance(stub_module, MixedObject), stub_module
+    assert isinstance(stub_module, (StubModuleContext, MixedObject)), stub_module
     non_stubs = stub_module.non_stub_context_set
     if ignore_compiled:
         non_stubs = non_stubs.filter(lambda c: not c.is_compiled())
diff --git a/test/test_api/test_interpreter.py b/test/test_api/test_interpreter.py
index 46056706..abee6b78 100644
--- a/test/test_api/test_interpreter.py
+++ b/test/test_api/test_interpreter.py
@@ -444,4 +444,3 @@ def test__wrapped__():
 def test_core_module_completes(module_name):
     module = import_module(module_name)
     assert jedi.Interpreter(module_name + '.\n', [locals()]).completions()
-