diff --git a/src/backend/executor/execExpr.c b/src/backend/executor/execExpr.c
index 0fb31f5c3d..9f83dbe51e 100644
--- a/src/backend/executor/execExpr.c
+++ b/src/backend/executor/execExpr.c
@@ -3009,8 +3009,9 @@ ExecBuildAggTrans(AggState *aggstate, AggStatePerPhase phase,
 			{
 				/*
 				 * Start from 1, since the 0th arg will be the transition
-				 * value
+				 * value. Exclude it from numTransInputs.
 				 */
+				pertrans->numTransInputs--;
 				ExecInitExprRec(source_tle->expr, state,
 								&trans_fcinfo->args[argno + 1].value,
 								&trans_fcinfo->args[argno + 1].isnull);