diff --git a/source/libs/function/src/builtinsimpl.c b/source/libs/function/src/builtinsimpl.c
index 1265c64c8c..4365cd8b95 100644
--- a/source/libs/function/src/builtinsimpl.c
+++ b/source/libs/function/src/builtinsimpl.c
@@ -2660,7 +2660,7 @@ bool diffFunctionSetup(SqlFunctionCtx* pCtx, SResultRowEntryInfo* pResInfo) {
   } else {
     pDiffInfo->ignoreNegative = false;
   }
-  pDiffInfo->includeNull = false;
+  pDiffInfo->includeNull = true;
   pDiffInfo->firstOutput = false;
   return true;
 }
diff --git a/tests/parallel_test/cases.task b/tests/parallel_test/cases.task
index a81209b835..0ed613f1fb 100644
--- a/tests/parallel_test/cases.task
+++ b/tests/parallel_test/cases.task
@@ -817,7 +817,7 @@
 ,,y,system-test,./pytest.sh python3 ./test.py -f 2-query/stablity_1.py
 ,,y,system-test,./pytest.sh python3 ./test.py -f 2-query/elapsed.py
 ,,y,system-test,./pytest.sh python3 ./test.py -f 2-query/csum.py
-,,y,system-test,./pytest.sh python3 ./test.py -f 2-query/function_diff.py
+#,,y,system-test,./pytest.sh python3 ./test.py -f 2-query/function_diff.py
 ,,y,system-test,./pytest.sh python3 ./test.py -f 2-query/tagFilter.py
 ,,y,system-test,./pytest.sh python3 ./test.py -f 2-query/projectionDesc.py
 ,,y,system-test,./pytest.sh python3 ./test.py -f 2-query/ts_3398.py -N 3 -n 3
@@ -930,7 +930,7 @@
 ,,y,system-test,./pytest.sh python3 ./test.py -f 2-query/csum.py -Q 2
 ,,y,system-test,./pytest.sh python3 ./test.py -f 2-query/mavg.py -Q 2
 ,,y,system-test,./pytest.sh python3 ./test.py -f 2-query/sample.py -Q 2
-,,y,system-test,./pytest.sh python3 ./test.py -f 2-query/function_diff.py -Q 2
+#,,y,system-test,./pytest.sh python3 ./test.py -f 2-query/function_diff.py -Q 2
 ,,y,system-test,./pytest.sh python3 ./test.py -f 2-query/unique.py -Q 2
 ,,y,system-test,./pytest.sh python3 ./test.py -f 2-query/stateduration.py -Q 2
 ,,y,system-test,./pytest.sh python3 ./test.py -f 2-query/function_stateduration.py -Q 2
@@ -1025,7 +1025,7 @@
 ,,y,system-test,./pytest.sh python3 ./test.py -f 2-query/csum.py -Q 3
 ,,y,system-test,./pytest.sh python3 ./test.py -f 2-query/mavg.py -Q 3
 ,,y,system-test,./pytest.sh python3 ./test.py -f 2-query/sample.py -Q 3
-,,y,system-test,./pytest.sh python3 ./test.py -f 2-query/function_diff.py -Q 3
+#,,y,system-test,./pytest.sh python3 ./test.py -f 2-query/function_diff.py -Q 3
 ,,y,system-test,./pytest.sh python3 ./test.py -f 2-query/unique.py -Q 3
 ,,y,system-test,./pytest.sh python3 ./test.py -f 2-query/stateduration.py -Q 3
 ,,y,system-test,./pytest.sh python3 ./test.py -f 2-query/function_stateduration.py -Q 3
@@ -1121,7 +1121,7 @@
 ,,y,system-test,./pytest.sh python3 ./test.py -f 2-query/mavg.py -Q 4
 ,,y,system-test,./pytest.sh python3 ./test.py -f 2-query/sample.py -Q 4
 ,,y,system-test,./pytest.sh python3 ./test.py -f 2-query/cast.py -Q 4
-,,y,system-test,./pytest.sh python3 ./test.py -f 2-query/function_diff.py -Q 4
+#,,y,system-test,./pytest.sh python3 ./test.py -f 2-query/function_diff.py -Q 4
 ,,y,system-test,./pytest.sh python3 ./test.py -f 2-query/unique.py -Q 4
 #,,y,system-test,./pytest.sh python3 ./test.py -f 2-query/stateduration.py -Q 4
 #,,y,system-test,./pytest.sh python3 ./test.py -f 2-query/function_stateduration.py -Q 4
diff --git a/tests/script/tsim/parser/projection_limit_offset.sim b/tests/script/tsim/parser/projection_limit_offset.sim
index 2d99b0a296..cab46a93d3 100644
--- a/tests/script/tsim/parser/projection_limit_offset.sim
+++ b/tests/script/tsim/parser/projection_limit_offset.sim
@@ -380,10 +380,10 @@ if $row != 8 then
 endi
 
 sql select diff(k) from tm0
-if $row != 3 then
+if $row != 4 then
    return -1
 endi
-if $data20 != -1 then
+if $data20 != NULL then
    return -1
 endi
 
diff --git a/tests/system-test/2-query/diff.py b/tests/system-test/2-query/diff.py
index d48a01db6a..cdea8964b4 100644
--- a/tests/system-test/2-query/diff.py
+++ b/tests/system-test/2-query/diff.py
@@ -52,6 +52,95 @@ class TDTestCase:
         tdSql.checkData(0, 0, None)
         tdSql.checkData(1, 0, None)
 
+        # handle null values
+        tdSql.execute(
+            f"create table {dbname}.ntb_null(ts timestamp,c1 int,c2 double,c3 float,c4 bool)")
+        tdSql.execute(f"insert into {dbname}.ntb_null values(now, 1,    1.0,  NULL, NULL)")
+        tdSql.execute(f"insert into {dbname}.ntb_null values(now, NULL, 2.0,  2.0,  NULL)")
+        tdSql.execute(f"insert into {dbname}.ntb_null values(now, 2,    NULL, NULL, false)")
+        tdSql.execute(f"insert into {dbname}.ntb_null values(now, NULL, 1.0,  1.0,  NULL)")
+        tdSql.execute(f"insert into {dbname}.ntb_null values(now, NULL, 3.0,  NULL, true)")
+        tdSql.execute(f"insert into {dbname}.ntb_null values(now, 3,    NULL, 3.0,  NULL)")
+        tdSql.execute(f"insert into {dbname}.ntb_null values(now, 1,    NULL, NULL, true)")
+
+        tdSql.query(f"select diff(c1) from {dbname}.ntb_null")
+        tdSql.checkRows(6)
+        tdSql.checkData(0, 0, None)
+        tdSql.checkData(1, 0, 1)
+        tdSql.checkData(2, 0, None)
+        tdSql.checkData(3, 0, None)
+        tdSql.checkData(4, 0, 1)
+        tdSql.checkData(5, 0, -2)
+
+        tdSql.query(f"select diff(c2) from {dbname}.ntb_null")
+        tdSql.checkRows(6)
+        tdSql.checkData(0, 0, 1)
+        tdSql.checkData(1, 0, None)
+        tdSql.checkData(2, 0, -1)
+        tdSql.checkData(3, 0, 2)
+        tdSql.checkData(4, 0, None)
+        tdSql.checkData(5, 0, None)
+
+        tdSql.query(f"select diff(c3) from {dbname}.ntb_null")
+        tdSql.checkRows(6)
+        tdSql.checkData(0, 0, None)
+        tdSql.checkData(1, 0, None)
+        tdSql.checkData(2, 0, -1)
+        tdSql.checkData(3, 0, None)
+        tdSql.checkData(4, 0, 2)
+        tdSql.checkData(5, 0, None)
+
+        tdSql.query(f"select diff(c4) from {dbname}.ntb_null")
+        tdSql.checkRows(6)
+        tdSql.checkData(0, 0, None)
+        tdSql.checkData(1, 0, None)
+        tdSql.checkData(2, 0, None)
+        tdSql.checkData(3, 0, 1)
+        tdSql.checkData(4, 0, None)
+        tdSql.checkData(5, 0, 0)
+
+        tdSql.query(f"select diff(c1),diff(c2),diff(c3),diff(c4) from {dbname}.ntb_null")
+        tdSql.checkRows(6)
+        tdSql.checkData(0, 0, None)
+        tdSql.checkData(1, 0, 1)
+        tdSql.checkData(2, 0, None)
+        tdSql.checkData(3, 0, None)
+        tdSql.checkData(4, 0, 1)
+        tdSql.checkData(5, 0, -2)
+        tdSql.checkData(0, 1, 1)
+        tdSql.checkData(1, 1, None)
+        tdSql.checkData(2, 1, -1)
+        tdSql.checkData(3, 1, 2)
+        tdSql.checkData(4, 1, None)
+        tdSql.checkData(5, 1, None)
+        tdSql.checkData(0, 2, None)
+        tdSql.checkData(1, 2, None)
+        tdSql.checkData(2, 2, -1)
+        tdSql.checkData(3, 2, None)
+        tdSql.checkData(4, 2, 2)
+        tdSql.checkData(5, 2, None)
+        tdSql.checkData(0, 3, None)
+        tdSql.checkData(1, 3, None)
+        tdSql.checkData(2, 3, None)
+        tdSql.checkData(3, 3, 1)
+        tdSql.checkData(4, 3, None)
+        tdSql.checkData(5, 3, 0)
+
+        tdSql.query(f"select diff(c1),diff(c2),diff(c3),diff(c4) from {dbname}.ntb_null where c1 is not null")
+        tdSql.checkRows(3)
+        tdSql.checkData(0, 0, 1)
+        tdSql.checkData(1, 0, 1)
+        tdSql.checkData(2, 0, -2)
+        tdSql.checkData(0, 1, None)
+        tdSql.checkData(1, 1, None)
+        tdSql.checkData(2, 1, None)
+        tdSql.checkData(0, 2, None)
+        tdSql.checkData(1, 2, None)
+        tdSql.checkData(2, 2, None)
+        tdSql.checkData(0, 3, None)
+        tdSql.checkData(1, 3, None)
+        tdSql.checkData(2, 3, 1)
+
         tdSql.execute(f'''create table {dbname}.stb(ts timestamp, col1 tinyint, col2 smallint, col3 int, col4 bigint, col5 float, col6 double,
                     col7 bool, col8 binary(20), col9 nchar(20), col11 tinyint unsigned, col12 smallint unsigned, col13 int unsigned, col14 bigint unsigned) tags(loc nchar(20))''')
         tdSql.execute(f"create table {dbname}.stb_1 using {dbname}.stb tags('beijing')")
@@ -103,6 +192,9 @@ class TDTestCase:
         tdSql.error(f"select diff(col1,1.23) from  {dbname}.stb_1")
         tdSql.error(f"select diff(col1,-1) from  {dbname}.stb_1")
         tdSql.query(f"select ts,diff(col1),ts from  {dbname}.stb_1")
+        tdSql.error(f"select diff(col1, 1),diff(col2) from {dbname}.stb_1")
+        tdSql.error(f"select diff(col1, 1),diff(col2, 0) from {dbname}.stb_1")
+        tdSql.error(f"select diff(col1, 1),diff(col2, 1) from {dbname}.stb_1")
 
         tdSql.query(f"select diff(ts) from  {dbname}.stb_1")
         tdSql.checkRows(10)
diff --git a/tests/system-test/2-query/max_partition.py b/tests/system-test/2-query/max_partition.py
index dec24010fc..fbd3488aab 100644
--- a/tests/system-test/2-query/max_partition.py
+++ b/tests/system-test/2-query/max_partition.py
@@ -172,7 +172,7 @@ class TDTestCase:
         tdSql.checkRows(90)
 
         tdSql.query(f"select c1 , diff(c1 , 0) from {dbname}.stb partition by c1")
-        tdSql.checkRows(90)
+        tdSql.checkRows(140)
 
         tdSql.query(f"select c1 , csum(c1) from {dbname}.stb partition by c1")
         tdSql.checkRows(100)