diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index 99aa0f0..0d54267 100644
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -2144,6 +2144,7 @@ ExplainTargetRel(Plan *plan, Index rti, ExplainState *es)
 		case T_BitmapHeapScan:
 		case T_TidScan:
 		case T_ForeignScan:
+		case T_CustomScan:
 		case T_ModifyTable:
 			/* Assert it's on a real relation */
 			Assert(rte->rtekind == RTE_RELATION);