diff --git a/src/backend/optimizer/plan/analyzejoins.c b/src/backend/optimizer/plan/analyzejoins.c
index d188d9724af..9b4c1033c93 100644
--- a/src/backend/optimizer/plan/analyzejoins.c
+++ b/src/backend/optimizer/plan/analyzejoins.c
@@ -345,6 +345,14 @@ join_is_removable(PlannerInfo *root, SpecialJoinInfo *sjinfo)
 			else
 				var = (Var *) get_leftop(rinfo->clause);
 
+			/*
+			 * We may ignore any RelabelType node above the operand.  (There
+			 * won't be more than one, since eval_const_expressions() has been
+			 * applied already.)
+			 */
+			if (var && IsA(var, RelabelType))
+				var = (Var *) ((RelabelType *) var)->arg;
+
 			/*
 			 * If inner side isn't a Var referencing a subquery output column,
 			 * this clause doesn't help us.