diff --git a/src/backend/executor/nodeAgg.c b/src/backend/executor/nodeAgg.c
index d01fc4f52e..7c6eab6d94 100644
--- a/src/backend/executor/nodeAgg.c
+++ b/src/backend/executor/nodeAgg.c
@@ -2935,7 +2935,7 @@ build_pertrans_for_aggref(AggStatePerTrans pertrans,
 		fmgr_info_set_expr((Node *) combinefnexpr, &pertrans->transfn);
 
 		pertrans->transfn_fcinfo =
-			(FunctionCallInfo) palloc(SizeForFunctionCallInfo(2));
+			(FunctionCallInfo) palloc(SizeForFunctionCallInfo(2) + 1);
 		InitFunctionCallInfoData(*pertrans->transfn_fcinfo,
 								 &pertrans->transfn,
 								 2,