diff --git a/src/client/src/tscFunctionImpl.c b/src/client/src/tscFunctionImpl.c
index a265243ce95c99da276e1396491303d7663c682e..81602d17f4560949d3cc7a9cce2e43eb6875302b 100644
--- a/src/client/src/tscFunctionImpl.c
+++ b/src/client/src/tscFunctionImpl.c
@@ -3158,7 +3158,7 @@ static void diff_function(SQLFunctionCtx *pCtx) {
           pOutput += 1;
           pTimestamp += 1;
         } else {
-          *pOutput = pData[i] - pCtx->param[1].i64Key;
+          *pOutput = pData[i] - pCtx->param[1].dKey;
           *pTimestamp = pCtx->ptsList[i];
           pOutput += 1;
           pTimestamp += 1;
@@ -3189,7 +3189,7 @@ static void diff_function(SQLFunctionCtx *pCtx) {
           pOutput += 1;
           pTimestamp += 1;
         } else {
-          *pOutput = pData[i] - pCtx->param[1].i64Key;
+          *pOutput = pData[i] - pCtx->param[1].dKey;
           *pTimestamp = pCtx->ptsList[i];
           
           pOutput += 1;