diff --git a/src/backend/columnar/cstore_fdw.c b/src/backend/columnar/cstore_fdw.c
index 97e6f5a3c..19b3d1847 100644
--- a/src/backend/columnar/cstore_fdw.c
+++ b/src/backend/columnar/cstore_fdw.c
@@ -718,7 +718,7 @@ FindCStoreTables(List *tableList)
 	foreach(relationCell, tableList)
 	{
 		RangeVar *rangeVar = (RangeVar *) lfirst(relationCell);
-		Oid relationId = RangeVarGetRelid(rangeVar, AccessShareLock, true);
+		Oid relationId = RangeVarGetRelid(rangeVar, NoLock, true);
 		if (IsCStoreFdwTable(relationId) && !DistributedTable(relationId))
 		{
 			cstoreTableList = lappend(cstoreTableList, rangeVar);
@@ -758,6 +758,17 @@ OpenRelationsForTruncate(List *cstoreTableList)
 		{
 			heap_close(relation, AccessExclusiveLock);
 		}
+
+		/*
+		 * Type of cstore tables can change since we checked last time,
+		 * since we didn't hold a lock when checking.
+		 */
+		else if (!IsCStoreFdwTable(relationId))
+		{
+			ereport(ERROR, (errmsg("relation \"%s\" not columnar anymore",
+								   RelationGetRelationName(relation)),
+							errhint("try repeating the truncate command")));
+		}
 		else
 		{
 			relationIdList = lappend_oid(relationIdList, relationId);
diff --git a/src/backend/columnar/cstore_tableam.c b/src/backend/columnar/cstore_tableam.c
index 203cbb334..d7c3aff11 100644
--- a/src/backend/columnar/cstore_tableam.c
+++ b/src/backend/columnar/cstore_tableam.c
@@ -58,7 +58,7 @@
  * These are the same values from src/backend/access/heap/vacuumlazy.c
  */
 #define VACUUM_TRUNCATE_LOCK_WAIT_INTERVAL 50       /* ms */
-#define VACUUM_TRUNCATE_LOCK_TIMEOUT 5000               /* ms */
+#define VACUUM_TRUNCATE_LOCK_TIMEOUT 4500               /* ms */
 
 typedef struct CStoreScanDescData
 {