diff --git a/src/backend/executor/execScan.c b/src/backend/executor/execScan.c
index a96e826..5c4a4f4 100644
--- a/src/backend/executor/execScan.c
+++ b/src/backend/executor/execScan.c
@@ -26,6 +26,32 @@
 static bool tlist_matches_tupdesc(PlanState *ps, List *tlist, Index varno, TupleDesc tupdesc);
 
 
+static Index
+get_proxy_scanrelid(ScanState *node)
+{
+	Scan	*scan = (Scan *) node->ps.plan;
+
+	Assert(scan->scanrelid == 0);
+
+	switch (nodeTag(scan))
+	{
+		case T_ForeignScan:
+			{
+				ForeignScan *fs = (ForeignScan *) scan;
+				return bms_first_member(fs->fs_relids);
+			}
+
+		case T_CustomScan:
+			{
+				CustomScan *cs = (CustomScan *) scan;
+				return bms_first_member(cs->custom_relids);
+			}
+
+		default:
+			elog(FATAL, "unexpected node type: %d", (int) nodeTag(scan));
+	}
+}
+
 /*
  * ExecScanFetch -- fetch next potential tuple
  *
@@ -49,6 +75,8 @@ ExecScanFetch(ScanState *node,
 		 */
 		Index		scanrelid = ((Scan *) node->ps.plan)->scanrelid;
 
+		if (scanrelid == 0)
+			scanrelid = get_proxy_scanrelid(node);
 		Assert(scanrelid > 0);
 		if (estate->es_epqTupleSet[scanrelid - 1])
 		{
@@ -347,6 +375,8 @@ ExecScanReScan(ScanState *node)
 	{
 		Index		scanrelid = ((Scan *) node->ps.plan)->scanrelid;
 
+		if (scanrelid == 0)
+			scanrelid = get_proxy_scanrelid(node);
 		Assert(scanrelid > 0);
 
 		estate->es_epqScanDone[scanrelid - 1] = false;