diff --git a/Objects/setobject.c b/Objects/setobject.c
index 154be43..31da3db 100644
--- a/Objects/setobject.c
+++ b/Objects/setobject.c
@@ -1710,8 +1710,10 @@
     if (otherset == NULL)
         return NULL;
     rv = set_symmetric_difference_update(otherset, (PyObject *)so);
-    if (rv == NULL)
+    if (rv == NULL) {
+        Py_DECREF(otherset);
         return NULL;
+    }
     Py_DECREF(rv);
     return (PyObject *)otherset;
 }