diff --git a/src/backend/distributed/deparser/ruleutils_17.c b/src/backend/distributed/deparser/ruleutils_17.c
index c96efb258..43720873b 100644
--- a/src/backend/distributed/deparser/ruleutils_17.c
+++ b/src/backend/distributed/deparser/ruleutils_17.c
@@ -1838,8 +1838,11 @@ set_deparse_plan(deparse_namespace *dpns, Plan *plan)
      * For a WorkTableScan, locate the parent RecursiveUnion plan node and use
      * that as INNER referent.
      *
-     * For MERGE, make the inner tlist point to the merge source tlist, which
-	 * is same as the targetlist that the ModifyTable's source plan provides.
+     * For MERGE, pretend the ModifyTable's source plan (its outer plan) is
+	 * INNER referent.  This is the join from the target relation to the data
+	 * source, and all INNER_VAR Vars in other parts of the query refer to its
+	 * targetlist.
+	 *
 	 * For ON CONFLICT .. UPDATE we just need the inner tlist to point to the
 	 * excluded expression's tlist. (Similar to the SubqueryScan we don't want
 	 * to reuse OUTER, it's used for RETURNING in some modify table cases,
@@ -1854,17 +1857,17 @@ set_deparse_plan(deparse_namespace *dpns, Plan *plan)
 		dpns->inner_plan = find_recursive_union(dpns,
 												(WorkTableScan *) plan);
 	else if (IsA(plan, ModifyTable))
-		dpns->inner_plan = plan;
+	{
+		if (((ModifyTable *) plan)->operation == CMD_MERGE)
+			dpns->inner_plan = outerPlan(plan);
+		else
+			dpns->inner_plan = plan;
+	}
 	else
 		dpns->inner_plan = innerPlan(plan);
 
-	if (IsA(plan, ModifyTable))
-	{
-		if (((ModifyTable *) plan)->operation == CMD_MERGE)
-			dpns->inner_tlist = dpns->outer_tlist;
-		else
-			dpns->inner_tlist = ((ModifyTable *) plan)->exclRelTlist;
-	}
+	if (IsA(plan, ModifyTable) && ((ModifyTable *) plan)->operation == CMD_INSERT)
+		dpns->inner_tlist = ((ModifyTable *) plan)->exclRelTlist;
 	else if (dpns->inner_plan)
 		dpns->inner_tlist = dpns->inner_plan->targetlist;
 	else