diff --git a/mindsdb/utilities/render/sqlalchemy_render.py b/mindsdb/utilities/render/sqlalchemy_render.py
index b07c34296d..9342877b5e 100644
--- a/mindsdb/utilities/render/sqlalchemy_render.py
+++ b/mindsdb/utilities/render/sqlalchemy_render.py
@@ -284,6 +284,15 @@ def to_expression(self, t):
             arg1 = self.to_expression(t.args[1])
 
             op = t.op.lower()
+            if (
+                op in ("is", "is not")
+                and isinstance(t.args[1], ast.Constant)
+                and t.args[1].value is None
+            ):
+                # to_expression wraps constants in a label; with a labeled NULL
+                # operand SQLAlchemy cannot negate the predicate, so NOT (x IS NULL)
+                # lost its NOT. A bare sa.null() keeps is_/is_not invertible.
+                arg1 = sa.null()
             if op in ("in", "not in"):
                 if t.args[1].parentheses:
                     arg1 = [arg1]
diff --git a/tests/unit/render/test_sqlalchemyrender.py b/tests/unit/render/test_sqlalchemyrender.py
index fd01bd4b2f..fc6de031d3 100644
--- a/tests/unit/render/test_sqlalchemyrender.py
+++ b/tests/unit/render/test_sqlalchemyrender.py
@@ -17,6 +17,21 @@
 
 
 class TestMysqlRender:
+    def test_not_is_null(self):
+        # NOT must survive rendering of negated IS [NOT] NULL predicates
+        # (regression: a labeled NULL operand made the inversion a no-op)
+        cases = {
+            "SELECT * FROM tb1 WHERE NOT (x IS NULL)": "SELECT * FROM tb1 WHERE x IS NOT NULL",
+            "SELECT * FROM tb1 WHERE NOT x IS NULL": "SELECT * FROM tb1 WHERE x IS NOT NULL",
+            "SELECT * FROM tb1 WHERE NOT (x IS NOT NULL)": "SELECT * FROM tb1 WHERE x IS NULL",
+            "SELECT * FROM tb1 WHERE x IS NULL": "SELECT * FROM tb1 WHERE x IS NULL",
+            "SELECT * FROM tb1 WHERE x IS NOT NULL": "SELECT * FROM tb1 WHERE x IS NOT NULL",
+        }
+        for sql_in, expected in cases.items():
+            query = parse_sql(sql_in)
+            sql = SqlalchemyRender("mysql").get_string(query, with_failback=False)
+            assert sql.replace("\n", "").replace("\t", "") == expected, sql_in
+
     def test_create_table(self):
         query = CreateTable(
             name="tbl1",