diff --git a/source/libs/function/src/builtinsimpl.c b/source/libs/function/src/builtinsimpl.c
index cdecc8b8cc..4c14b67155 100644
--- a/source/libs/function/src/builtinsimpl.c
+++ b/source/libs/function/src/builtinsimpl.c
@@ -2663,7 +2663,7 @@ bool diffFunctionSetup(SqlFunctionCtx* pCtx, SResultRowEntryInfo* pResInfo) {
   } else {
     pDiffInfo->ignoreNegative = false;
   }
-  pDiffInfo->includeNull = false;
+  pDiffInfo->includeNull = true;
   pDiffInfo->firstOutput = false;
   return true;
 }