diff --git a/src/backend/commands/indexcmds.c b/src/backend/commands/indexcmds.c
index 3fb2344198..51dadb04cf 100644
--- a/src/backend/commands/indexcmds.c
+++ b/src/backend/commands/indexcmds.c
@@ -182,9 +182,13 @@ CheckIndexCompatible(Oid oldId,
 	 * the new index, so we can test whether it's compatible with the existing
 	 * one.  Note that ComputeIndexAttrs might fail here, but that's OK:
 	 * DefineIndex would have called this function with the same arguments
-	 * later on, and it would have failed then anyway.
+	 * later on, and it would have failed then anyway.  Our attributeList
+	 * contains only key attributes, thus we're filling ii_NumIndexAttrs and
+	 * ii_NumIndexKeyAttrs with same value.
 	 */
 	indexInfo = makeNode(IndexInfo);
+	indexInfo->ii_NumIndexAttrs = numberOfAttributes;
+	indexInfo->ii_NumIndexKeyAttrs = numberOfAttributes;
 	indexInfo->ii_Expressions = NIL;
 	indexInfo->ii_ExpressionsState = NIL;
 	indexInfo->ii_PredicateState = NULL;
@@ -1523,6 +1527,7 @@ ComputeIndexAttrs(IndexInfo *indexInfo,
 		if (attn >= nkeycols)
 		{
 			colOptionP[attn] = 0;
+			classOidP[attn] = InvalidOid;
 			attn++;
 			continue;
 		}