diff --git a/src/backend/replication/logical/conflict.c b/src/backend/replication/logical/conflict.c
index f0b71a74d89..a286f616f9c 100644
--- a/src/backend/replication/logical/conflict.c
+++ b/src/backend/replication/logical/conflict.c
@@ -1138,7 +1138,11 @@ build_index_key_json(EState *estate, Relation localrel,
 				continue;
 			}
 
-			getTypeOutputInfo(att->atttypid, &outfuncoid, &typisvarlena);
+			/*
+			 * See BuildIndexValueDescription() for why we used
+			 * rd_opcintype instead index's tupleDesc.
+			 */
+			getTypeOutputInfo(indexDesc->rd_opcintype[i], &outfuncoid, &typisvarlena);
 			outputstr = OidOutputFunctionCall(outfuncoid, values[i]);
 			escape_json(&result, outputstr);
 			pfree(outputstr);