diff --git a/src/backend/optimizer/path/indxpath.c b/src/backend/optimizer/path/indxpath.c
index cc607dcdfa..ca9e067450 100644
--- a/src/backend/optimizer/path/indxpath.c
+++ b/src/backend/optimizer/path/indxpath.c
@@ -2245,7 +2245,7 @@ match_clause_to_index(IndexOptInfo *index,
 		return;
 
 	/* OK, check each index column for a match */
-	for (indexcol = 0; indexcol < index->ncolumns; indexcol++)
+	for (indexcol = 0; indexcol < index->nkeycolumns; indexcol++)
 	{
 		if (match_clause_to_indexcol(index,
 									 indexcol,