diff --git a/src/common/backend/catalog/namespace.cpp b/src/common/backend/catalog/namespace.cpp
index 44774bda08b6cf59014200bf073d4cf3b670a196..605cea1000fa0a7283fd1cb708daf3f829a86f17 100644
--- a/src/common/backend/catalog/namespace.cpp
+++ b/src/common/backend/catalog/namespace.cpp
@@ -334,7 +334,14 @@ Oid RangeVarGetRelidExtended(const RangeVar* relation, LOCKMODE lockmode, bool m
                 errDetail = RelnameGetRelidExtended(relation->relname, &relId, refSynOid, detailInfo);
                 if (OidIsValid(relId)) {
                     Oid namespaceId = get_rel_namespace(relId);
-                    LookupExplicitNamespace(get_namespace_name(namespaceId));
+                    char* nspname = get_namespace_name(namespaceId);
+                    if (nspname) {
+                        LookupExplicitNamespace(nspname);
+                        pfree(nspname);
+                    } else {
+                        ereport(ERROR, (errmodule(MOD_SEC), errcode(ERRCODE_UNDEFINED_SCHEMA),
+                            errmsg("schema with OID %u does not exist", namespaceId)));
+                    }
                 }
             } else {
                 relId = RelnameGetRelid(relation->relname, detailInfo);