diff --git a/src/backend/optimizer/util/plancat.c b/src/backend/optimizer/util/plancat.c
index b73bc574bf7..04d20485713 100644
--- a/src/backend/optimizer/util/plancat.c
+++ b/src/backend/optimizer/util/plancat.c
@@ -1068,12 +1068,12 @@ infer_arbiter_indexes(PlannerInfo *root)
 		{
 			int			attno = idxRel->rd_index->indkey.values[natt];
 
-			if (attno == 0)
+			if (attno == InvalidAttrNumber)
 			{
 				Node	   *expr = (Node *) lfirst(idxExprCell);
 
 				idxExprCell = lnext(idxExprs, idxExprCell);
-				if (!IsA(expr, Var) || ((Var *) expr)->varattno == 0)
+				if (!IsA(expr, Var) || ((Var *) expr)->varattno == InvalidAttrNumber)
 				{
 					idxOtherExprs = lappend(idxOtherExprs, expr);
 					continue;
@@ -1264,7 +1264,7 @@ infer_collation_opclass_match(InferenceElem *elem, Relation idxRel,
 		}
 
 		/* If one matching index att found, good enough -- return true */
-		if (attno != 0)
+		if (attno != InvalidAttrNumber)
 		{
 			if (IsA(elem->expr, Var) &&
 				((Var *) elem->expr)->varattno == attno)