diff --git a/Python/ceval.c b/Python/ceval.c
index 5c3bb83..f0ea7c9 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -3413,6 +3413,13 @@
         value = PyObject_CallObject(exc, NULL);
         if (value == NULL)
             goto raise_error;
+        if (!PyExceptionInstance_Check(value)) {
+            PyErr_Format(PyExc_TypeError,
+                         "calling %R should have returned an instance of "
+                         "BaseException, not %R",
+                         type, Py_TYPE(value));
+            goto raise_error;
+        }
     }
     else if (PyExceptionInstance_Check(exc)) {
         value = exc;