Index: modules/dav/main/util.c
===================================================================
--- modules/dav/main/util.c	(revision 1871937)
+++ modules/dav/main/util.c	(working copy)
@@ -1667,6 +1667,7 @@
                 }
 
                 /* assert: DAV_VALIDATE_PARENT implies response != NULL */
+                AP_DEBUG_ASSERT(response != NULL);
                 new_response->next = *response;
                 *response = new_response;