src/backend/executor/execScan.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/src/backend/executor/execScan.c b/src/backend/executor/execScan.c
index a96e826..89c75ca 100644
--- a/src/backend/executor/execScan.c
+++ b/src/backend/executor/execScan.c
@@ -49,8 +49,19 @@ ExecScanFetch(ScanState *node,
 		 */
 		Index		scanrelid = ((Scan *) node->ps.plan)->scanrelid;
 
-		Assert(scanrelid > 0);
-		if (estate->es_epqTupleSet[scanrelid - 1])
+		if (scanrelid == 0)
+		{
+			TupleTableSlot	   *slot = ExecClearTuple(node->ss_ScanTupleSlot);
+
+			/* Only ForeignScan or CustomScan can have scanrelid==0 */
+			Assert(IsA(node, ForeignScanState) ||
+				   IsA(node, CustomScanState));
+			/* Check if it meets the access-method conditions */
+			if (!(*recheckMtd) (node, slot))
+				ExecClearTuple(slot);	/* ensure an empty slot is returned */
+			return slot;
+		}
+		else if (estate->es_epqTupleSet[scanrelid - 1])
 		{
 			TupleTableSlot *slot = node->ss_ScanTupleSlot;