diff --git a/src/if_py_both.h b/src/if_py_both.h
index cd80800..2739f66 100644
--- a/src/if_py_both.h
+++ b/src/if_py_both.h
@@ -738,6 +738,8 @@
     tv->vval.v_dict = d;
 
     list = PyMapping_Items(obj);
+    if (list == NULL)
+	return -1;
     lsize = PyList_Size(list);
     while (lsize--)
     {