diff --git a/src/backend/catalog/index.c b/src/backend/catalog/index.c
index 5d73e92901..0002816fcc 100644
--- a/src/backend/catalog/index.c
+++ b/src/backend/catalog/index.c
@@ -1831,6 +1831,10 @@ CompareIndexInfo(IndexInfo *info1, IndexInfo *info2,
 	if (info1->ii_NumIndexAttrs != info2->ii_NumIndexAttrs)
 		return false;
 
+	/* and same number of key attributes */
+	if (info1->ii_NumIndexKeyAttrs != info2->ii_NumIndexKeyAttrs)
+		return false;
+
 	/*
 	 * and columns match through the attribute map (actual attribute numbers
 	 * might differ!)  Note that this implies that index columns that are
@@ -1850,7 +1854,9 @@ CompareIndexInfo(IndexInfo *info1, IndexInfo *info2,
 
 		if (collations1[i] != collations2[i])
 			return false;
-		if (opfamilies1[i] != opfamilies2[i])
+
+		/* opfamily is valid on for key attributes */
+		if (i < info2->ii_NumIndexKeyAttrs && opfamilies1[i] != opfamilies2[i])
 			return false;
 	}