carljm · Jun 9, 2026 · Jun 1, 2026 · Jun 1, 2026 · Jun 1, 2026 · Jun 1, 2026
diff --git a/Lib/test/test_listcomps.py b/Lib/test/test_listcomps.py
@@ -171,6 +171,22 @@ def test_references___class__(self):
         """
         self._check_in_scopes(code, raises=NameError)
 
+    def test_lambda_in_comprehension_references___class__(self):
+        # gh-150700: lambda in class-scope comprehension referencing __class__
+        # must compile without SystemError and raise NameError at runtime
+        # (__class__ cell is not yet filled during class body execution).
+        code = """
+            res = [(lambda: __class__)() for _ in [1]]
+        """
+        self._check_in_scopes(code, raises=NameError)
+
+    def test_lambda_in_comprehension_references___classdict__(self):
+        # gh-150700: lambda in class-scope comprehension referencing __classdict__
+        # must compile without SystemError; __classdict__ is available at runtime.
+        class _C:
+            res = [(lambda: __classdict__)() for _ in [1]]
+        self.assertIn("res", _C.res[0])
+
     def test_references___class___defined(self):
         code = """
             __class__ = 2

diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2026-06-01-19-00-00.gh-issue-150700.W8CzVR.rst b/Misc/NEWS.d/next/Core_and_Builtins/2026-06-01-19-00-00.gh-issue-150700.W8CzVR.rst
@@ -0,0 +1,3 @@
+Fix a :exc:`SystemError` when compiling a class-scope comprehension containing
+a ``lambda`` that references ``__class__``, ``__classdict__``, or
+``__conditional_annotations__``. Patch by Bartosz Sławecki.
@@ -834,17 +834,22 @@ inline_comprehension(PySTEntryObject *ste, PySTEntryObject *comp,
             return 0;
         }
         // __class__, __classdict__ and __conditional_annotations__ are
-        // never allowed to be free through a class scope (see
-        // drop_class_free)
+        // not allowed to be free through a class scope (see
+        // drop_class_free) unless children scopes need it
         if (scope == FREE && ste->ste_type == ClassBlock &&
                 (_PyUnicode_EqualToASCIIString(k, "__class__") ||
                  _PyUnicode_EqualToASCIIString(k, "__classdict__") ||
                  _PyUnicode_EqualToASCIIString(k, "__conditional_annotations__"))) {
             scope = GLOBAL_IMPLICIT;
-            if (PySet_Discard(comp_free, k) < 0) {
+            int child_needs_free = is_free_in_any_child(comp, k);
+            if (child_needs_free < 0) {
                 return 0;
             }
-
+            if (!child_needs_free) {
+                if (PySet_Discard(comp_free, k) < 0) {
+                    return 0;
+                }
+            }
             if (_PyUnicode_EqualToASCIIString(k, "__class__")) {
                 remove_dunder_class = 1;
             }