--- 2.2.21/modules/dav/fs/dbm.c	(revision 14744)
+++ 2.2.21/modules/dav/fs/dbm.c	(revision 14745)
@@ -191,8 +191,16 @@ void dav_dbm_close(dav_db *db)
 
 dav_error * dav_dbm_fetch(dav_db *db, apr_datum_t key, apr_datum_t *pvalue)
 {
-    apr_status_t status = apr_dbm_fetch(db->file, key, pvalue);
+    apr_status_t status;
 
+    if (key.dptr == NULL) {
+        /* no key could be created (namespace not known) => no value */
+        memset(pvalue, 0, sizeof(*pvalue));
+        status = APR_SUCCESS;
+    } else {
+        status = apr_dbm_fetch(db->file, key, pvalue);
+    }
+
     return dav_fs_dbm_error(db, NULL, status);
 }