diff --git a/mypyc/irbuild/callable_class.py b/mypyc/irbuild/callable_class.py
index 9ca1318a843f..1b850f57d231 100644
--- a/mypyc/irbuild/callable_class.py
+++ b/mypyc/irbuild/callable_class.py
@@ -78,6 +78,9 @@ class for the nested function.
     # this is a toplevel lambda), don't set up an environment.
     if builder.fn_infos[-2].contains_nested:
         callable_class_ir.attributes[ENV_ATTR_NAME] = RInstance(builder.fn_infos[-2].env_class)
+        # The link is initialized before the callable is published and is never rebound.
+        # Treating it as Final permits plain loads on free-threaded builds.
+        callable_class_ir.final_attributes.add(ENV_ATTR_NAME)
     callable_class_ir.mro = [callable_class_ir]
     builder.fn_info.callable_class = ImplicitClass(callable_class_ir)
     builder.classes.append(callable_class_ir)
@@ -235,7 +238,11 @@ def instantiate_callable_class(builder: IRBuilder, fn_info: FuncInfo) -> Value:
     elif builder.fn_info.contains_nested:
         curr_env_reg = builder.fn_info.curr_env_reg
     if curr_env_reg:
-        builder.add(SetAttr(func_reg, ENV_ATTR_NAME, curr_env_reg, fitem.line))
+        set_env = SetAttr(func_reg, ENV_ATTR_NAME, curr_env_reg, fitem.line)
+        # A new or freelist-reused callable has had all of its fields cleared, and this store
+        # happens before the callable can escape.
+        set_env.mark_as_initializer()
+        builder.add(set_env)
     # Initialize function wrapper for callable classes. As opposed to regular functions,
     # each instance of a callable class needs its own wrapper because they might be instantiated
     # inside other functions.
diff --git a/mypyc/test-data/irbuild-basic.test b/mypyc/test-data/irbuild-basic.test
index 55bf15014916..113b7b826c27 100644
--- a/mypyc/test-data/irbuild-basic.test
+++ b/mypyc/test-data/irbuild-basic.test
@@ -2475,13 +2475,12 @@ def a(f):
     r0 :: __main__.a_env
     r1 :: bool
     r2 :: __main__.g_a_obj
-    r3 :: bool
     g :: object
 L0:
     r0 = a_env()
     r0.f = f; r1 = is_error
     r2 = g_a_obj()
-    r2.__mypyc_env__ = r0; r3 = is_error
+    r2.__mypyc_env__ = r0
     g = r2
     return g
 def g_b_obj.__get__(__mypyc_self__, instance, owner):
@@ -2540,13 +2539,12 @@ def b(f):
     r0 :: __main__.b_env
     r1 :: bool
     r2 :: __main__.g_b_obj
-    r3 :: bool
     g :: object
 L0:
     r0 = b_env()
     r0.f = f; r1 = is_error
     r2 = g_b_obj()
-    r2.__mypyc_env__ = r0; r3 = is_error
+    r2.__mypyc_env__ = r0
     g = r2
     return g
 def d_c_obj.__get__(__mypyc_self__, instance, owner):
@@ -2586,62 +2584,61 @@ L0:
 def c():
     r0 :: __main__.c_env
     r1 :: __main__.d_c_obj
-    r2 :: bool
-    r3 :: dict
-    r4 :: str
-    r5 :: object
-    r6 :: object[1]
-    r7 :: object_ptr
-    r8 :: object
-    r9 :: dict
-    r10 :: str
-    r11 :: object
-    r12 :: object[1]
-    r13 :: object_ptr
-    r14, d :: object
-    r15 :: dict
-    r16 :: str
-    r17 :: i32
-    r18 :: bit
-    r19 :: str
-    r20 :: object
-    r21 :: str
-    r22 :: object
-    r23 :: object[1]
-    r24 :: object_ptr
-    r25, r26 :: object
+    r2 :: dict
+    r3 :: str
+    r4 :: object
+    r5 :: object[1]
+    r6 :: object_ptr
+    r7 :: object
+    r8 :: dict
+    r9 :: str
+    r10 :: object
+    r11 :: object[1]
+    r12 :: object_ptr
+    r13, d :: object
+    r14 :: dict
+    r15 :: str
+    r16 :: i32
+    r17 :: bit
+    r18 :: str
+    r19 :: object
+    r20 :: str
+    r21 :: object
+    r22 :: object[1]
+    r23 :: object_ptr
+    r24, r25 :: object
 L0:
     r0 = c_env()
     r1 = d_c_obj()
-    r1.__mypyc_env__ = r0; r2 = is_error
-    r3 = __main__.globals :: static
-    r4 = 'b'
-    r5 = CPyDict_GetItem(r3, r4)
-    r6 = [r1]
-    r7 = load_address r6
-    r8 = PyObject_Vectorcall(r5, r7, 1, 0)
+    r1.__mypyc_env__ = r0
+    r2 = __main__.globals :: static
+    r3 = 'b'
+    r4 = CPyDict_GetItem(r2, r3)
+    r5 = [r1]
+    r6 = load_address r5
+    r7 = PyObject_Vectorcall(r4, r6, 1, 0)
     keep_alive r1
-    r9 = __main__.globals :: static
-    r10 = 'a'
-    r11 = CPyDict_GetItem(r9, r10)
-    r12 = [r8]
-    r13 = load_address r12
-    r14 = PyObject_Vectorcall(r11, r13, 1, 0)
-    keep_alive r8
-    d = r14
-    r15 = __main__.globals :: static
-    r16 = 'd'
-    r17 = PyDict_SetItem(r15, r16, r14)
-    r18 = r17 >= 0 :: signed
-    r19 = 'c'
-    r20 = builtins :: module
-    r21 = 'print'
-    r22 = CPyObject_GetAttr(r20, r21)
-    r23 = [r19]
-    r24 = load_address r23
-    r25 = PyObject_Vectorcall(r22, r24, 1, 0)
-    keep_alive r19
-    r26 = PyObject_Vectorcall(d, 0, 0, 0)
+    r8 = __main__.globals :: static
+    r9 = 'a'
+    r10 = CPyDict_GetItem(r8, r9)
+    r11 = [r7]
+    r12 = load_address r11
+    r13 = PyObject_Vectorcall(r10, r12, 1, 0)
+    keep_alive r7
+    d = r13
+    r14 = __main__.globals :: static
+    r15 = 'd'
+    r16 = PyDict_SetItem(r14, r15, r13)
+    r17 = r16 >= 0 :: signed
+    r18 = 'c'
+    r19 = builtins :: module
+    r20 = 'print'
+    r21 = CPyObject_GetAttr(r19, r20)
+    r22 = [r18]
+    r23 = load_address r22
+    r24 = PyObject_Vectorcall(r21, r23, 1, 0)
+    keep_alive r18
+    r25 = PyObject_Vectorcall(d, 0, 0, 0)
     return 1
 def __top_level__():
     r0, r1 :: object
@@ -2775,13 +2772,12 @@ def a(f):
     r0 :: __main__.a_env
     r1 :: bool
     r2 :: __main__.g_a_obj
-    r3 :: bool
     g :: object
 L0:
     r0 = a_env()
     r0.f = f; r1 = is_error
     r2 = g_a_obj()
-    r2.__mypyc_env__ = r0; r3 = is_error
+    r2.__mypyc_env__ = r0
     g = r2
     return g
 def __top_level__():
@@ -3588,13 +3584,12 @@ def deco(fn):
     r0 :: __main__.deco_env
     r1 :: bool
     r2 :: __main__.wrapper_deco_obj
-    r3 :: bool
     wrapper :: object
 L0:
     r0 = deco_env()
     r0.fn = fn; r1 = is_error
     r2 = wrapper_deco_obj()
-    r2.__mypyc_env__ = r0; r3 = is_error
+    r2.__mypyc_env__ = r0
     wrapper = r2
     return wrapper
 
@@ -3637,13 +3632,12 @@ def deco(fn):
     r0 :: __main__.deco_env
     r1 :: bool
     r2 :: __main__.wrapper_deco_obj
-    r3 :: bool
     wrapper :: object
 L0:
     r0 = deco_env()
     r0.fn = fn; r1 = is_error
     r2 = wrapper_deco_obj()
-    r2.__mypyc_env__ = r0; r3 = is_error
+    r2.__mypyc_env__ = r0
     wrapper = r2
     return wrapper
 
@@ -3689,13 +3683,12 @@ def deco(fn):
     r0 :: __main__.deco_env
     r1 :: bool
     r2 :: __main__.wrapper_deco_obj
-    r3 :: bool
     wrapper :: object
 L0:
     r0 = deco_env()
     r0.fn = fn; r1 = is_error
     r2 = wrapper_deco_obj()
-    r2.__mypyc_env__ = r0; r3 = is_error
+    r2.__mypyc_env__ = r0
     wrapper = r2
     return wrapper
 
@@ -3738,13 +3731,12 @@ def deco(fn):
     r0 :: __main__.deco_env
     r1 :: bool
     r2 :: __main__.wrapper_deco_obj
-    r3 :: bool
     wrapper :: object
 L0:
     r0 = deco_env()
     r0.fn = fn; r1 = is_error
     r2 = wrapper_deco_obj()
-    r2.__mypyc_env__ = r0; r3 = is_error
+    r2.__mypyc_env__ = r0
     wrapper = r2
     return wrapper
 
@@ -3790,13 +3782,12 @@ def deco(fn):
     r0 :: __main__.deco_env
     r1 :: bool
     r2 :: __main__.wrapper_deco_obj
-    r3 :: bool
     wrapper :: object
 L0:
     r0 = deco_env()
     r0.fn = fn; r1 = is_error
     r2 = wrapper_deco_obj()
-    r2.__mypyc_env__ = r0; r3 = is_error
+    r2.__mypyc_env__ = r0
     wrapper = r2
     return wrapper
 
diff --git a/mypyc/test-data/irbuild-generics.test b/mypyc/test-data/irbuild-generics.test
index 0d4dad4f97e2..66f4a2914ee6 100644
--- a/mypyc/test-data/irbuild-generics.test
+++ b/mypyc/test-data/irbuild-generics.test
@@ -178,7 +178,6 @@ def f(x):
     x :: int
 L0:
     return x
-
 [case testTypeVarMappingBound]
 # Dicts are special-cased for efficient iteration.
 from typing import Dict, TypedDict, TypeVar, Union
@@ -760,13 +759,12 @@ def deco(func):
     r0 :: __main__.deco_env
     r1 :: bool
     r2 :: __main__.inner_deco_obj
-    r3 :: bool
     inner :: object
 L0:
     r0 = deco_env()
     r0.func = func; r1 = is_error
     r2 = inner_deco_obj()
-    r2.__mypyc_env__ = r0; r3 = is_error
+    r2.__mypyc_env__ = r0
     inner = r2
     return inner
 def f(x):
diff --git a/mypyc/test-data/irbuild-nested.test b/mypyc/test-data/irbuild-nested.test
index 1b390e9c3504..be5129aa2b8c 100644
--- a/mypyc/test-data/irbuild-nested.test
+++ b/mypyc/test-data/irbuild-nested.test
@@ -58,12 +58,11 @@ L0:
 def a():
     r0 :: __main__.a_env
     r1 :: __main__.inner_a_obj
-    r2 :: bool
     inner :: object
 L0:
     r0 = a_env()
     r1 = inner_a_obj()
-    r1.__mypyc_env__ = r0; r2 = is_error
+    r1.__mypyc_env__ = r0
     inner = r1
     return inner
 def second_b_first_obj.__get__(__mypyc_self__, instance, owner):
@@ -108,25 +107,23 @@ def first_b_obj.__call__(__mypyc_self__):
     r1 :: __main__.first_b_env
     r2 :: bool
     r3 :: __main__.second_b_first_obj
-    r4 :: bool
     second :: object
 L0:
     r0 = __mypyc_self__.__mypyc_env__
     r1 = first_b_env()
     r1.__mypyc_env__ = r0; r2 = is_error
     r3 = second_b_first_obj()
-    r3.__mypyc_env__ = r1; r4 = is_error
+    r3.__mypyc_env__ = r1
     second = r3
     return second
 def b():
     r0 :: __main__.b_env
     r1 :: __main__.first_b_obj
-    r2 :: bool
     first :: object
 L0:
     r0 = b_env()
     r1 = first_b_obj()
-    r1.__mypyc_env__ = r0; r2 = is_error
+    r1.__mypyc_env__ = r0
     first = r1
     return first
 def inner_c_obj.__get__(__mypyc_self__, instance, owner):
@@ -156,12 +153,11 @@ def c(num):
     num :: float
     r0 :: __main__.c_env
     r1 :: __main__.inner_c_obj
-    r2 :: bool
     inner :: object
 L0:
     r0 = c_env()
     r1 = inner_c_obj()
-    r1.__mypyc_env__ = r0; r2 = is_error
+    r1.__mypyc_env__ = r0
     inner = r1
     return inner
 def inner_d_obj.__get__(__mypyc_self__, instance, owner):
@@ -191,36 +187,35 @@ def d(num):
     num :: float
     r0 :: __main__.d_env
     r1 :: __main__.inner_d_obj
-    r2 :: bool
     inner :: object
-    r3 :: str
-    r4 :: object[1]
-    r5 :: object_ptr
-    r6 :: object
-    r7, a, r8 :: str
-    r9 :: object[1]
-    r10 :: object_ptr
-    r11 :: object
-    r12, b :: str
+    r2 :: str
+    r3 :: object[1]
+    r4 :: object_ptr
+    r5 :: object
+    r6, a, r7 :: str
+    r8 :: object[1]
+    r9 :: object_ptr
+    r10 :: object
+    r11, b :: str
 L0:
     r0 = d_env()
     r1 = inner_d_obj()
-    r1.__mypyc_env__ = r0; r2 = is_error
+    r1.__mypyc_env__ = r0
     inner = r1
-    r3 = 'one'
-    r4 = [r3]
-    r5 = load_address r4
-    r6 = PyObject_Vectorcall(inner, r5, 1, 0)
-    keep_alive r3
-    r7 = cast(str, r6)
-    a = r7
-    r8 = 'two'
-    r9 = [r8]
-    r10 = load_address r9
-    r11 = PyObject_Vectorcall(inner, r10, 1, 0)
-    keep_alive r8
-    r12 = cast(str, r11)
-    b = r12
+    r2 = 'one'
+    r3 = [r2]
+    r4 = load_address r3
+    r5 = PyObject_Vectorcall(inner, r4, 1, 0)
+    keep_alive r2
+    r6 = cast(str, r5)
+    a = r6
+    r7 = 'two'
+    r8 = [r7]
+    r9 = load_address r8
+    r10 = PyObject_Vectorcall(inner, r9, 1, 0)
+    keep_alive r7
+    r11 = cast(str, r10)
+    b = r11
     return a
 def inner():
     r0 :: str
@@ -291,18 +286,17 @@ def a(num):
     r0 :: __main__.a_env
     r1 :: bool
     r2 :: __main__.inner_a_obj
-    r3 :: bool
-    inner, r4 :: object
-    r5 :: int
+    inner, r3 :: object
+    r4 :: int
 L0:
     r0 = a_env()
     r0.num = num; r1 = is_error
     r2 = inner_a_obj()
-    r2.__mypyc_env__ = r0; r3 = is_error
+    r2.__mypyc_env__ = r0
     inner = r2
-    r4 = PyObject_Vectorcall(inner, 0, 0, 0)
-    r5 = unbox(int, r4)
-    return r5
+    r3 = PyObject_Vectorcall(inner, 0, 0, 0)
+    r4 = unbox(int, r3)
+    return r4
 def inner_b_obj.__get__(__mypyc_self__, instance, owner):
     __mypyc_self__, instance, owner, r0 :: object
     r1 :: bit
@@ -331,20 +325,19 @@ def b():
     r0 :: __main__.b_env
     r1 :: bool
     r2 :: __main__.inner_b_obj
-    r3 :: bool
-    inner, r4 :: object
-    r5, r6, r7 :: int
+    inner, r3 :: object
+    r4, r5, r6 :: int
 L0:
     r0 = b_env()
     r0.num = 6; r1 = is_error
     r2 = inner_b_obj()
-    r2.__mypyc_env__ = r0; r3 = is_error
+    r2.__mypyc_env__ = r0
     inner = r2
-    r4 = PyObject_Vectorcall(inner, 0, 0, 0)
-    r5 = unbox(int, r4)
-    r6 = r0.num
-    r7 = CPyTagged_Add(r5, r6)
-    return r7
+    r3 = PyObject_Vectorcall(inner, 0, 0, 0)
+    r4 = unbox(int, r3)
+    r5 = r0.num
+    r6 = CPyTagged_Add(r4, r5)
+    return r6
 def inner_c_obj.__get__(__mypyc_self__, instance, owner):
     __mypyc_self__, instance, owner, r0 :: object
     r1 :: bit
@@ -391,28 +384,26 @@ def c(flag):
     flag :: bool
     r0 :: __main__.c_env
     r1 :: __main__.inner_c_obj
-    r2 :: bool
     inner :: object
-    r3 :: __main__.inner_c_obj_0
-    r4 :: bool
-    r5 :: object
-    r6 :: str
+    r2 :: __main__.inner_c_obj_0
+    r3 :: object
+    r4 :: str
 L0:
     r0 = c_env()
     if flag goto L1 else goto L2 :: bool
 L1:
     r1 = inner_c_obj()
-    r1.__mypyc_env__ = r0; r2 = is_error
+    r1.__mypyc_env__ = r0
     inner = r1
     goto L3
 L2:
-    r3 = inner_c_obj_0()
-    r3.__mypyc_env__ = r0; r4 = is_error
-    inner = r3
+    r2 = inner_c_obj_0()
+    r2.__mypyc_env__ = r0
+    inner = r2
 L3:
-    r5 = PyObject_Vectorcall(inner, 0, 0, 0)
-    r6 = cast(str, r5)
-    return r6
+    r3 = PyObject_Vectorcall(inner, 0, 0, 0)
+    r4 = cast(str, r3)
+    return r4
 
 [case testSpecialNested]
 def a() -> int:
@@ -469,9 +460,8 @@ def b_a_obj.__call__(__mypyc_self__):
     r3, r4 :: int
     r5 :: bool
     r6 :: __main__.c_a_b_obj
-    r7 :: bool
-    c, r8 :: object
-    r9 :: int
+    c, r7 :: object
+    r8 :: int
 L0:
     r0 = __mypyc_self__.__mypyc_env__
     r1 = b_a_env()
@@ -480,27 +470,26 @@ L0:
     r4 = CPyTagged_Add(r3, 2)
     r0.x = r4; r5 = is_error
     r6 = c_a_b_obj()
-    r6.__mypyc_env__ = r1; r7 = is_error
+    r6.__mypyc_env__ = r1
     c = r6
-    r8 = PyObject_Vectorcall(c, 0, 0, 0)
-    r9 = unbox(int, r8)
-    return r9
+    r7 = PyObject_Vectorcall(c, 0, 0, 0)
+    r8 = unbox(int, r7)
+    return r8
 def a():
     r0 :: __main__.a_env
     r1 :: bool
     r2 :: __main__.b_a_obj
-    r3 :: bool
-    b, r4 :: object
-    r5 :: int
+    b, r3 :: object
+    r4 :: int
 L0:
     r0 = a_env()
     r0.x = 2; r1 = is_error
     r2 = b_a_obj()
-    r2.__mypyc_env__ = r0; r3 = is_error
+    r2.__mypyc_env__ = r0
     b = r2
-    r4 = PyObject_Vectorcall(b, 0, 0, 0)
-    r5 = unbox(int, r4)
-    return r5
+    r3 = PyObject_Vectorcall(b, 0, 0, 0)
+    r4 = unbox(int, r3)
+    return r4
 
 [case testNestedFunctionInsideStatements]
 def f(flag: bool) -> str:
@@ -558,28 +547,26 @@ def f(flag):
     flag :: bool
     r0 :: __main__.f_env
     r1 :: __main__.inner_f_obj
-    r2 :: bool
     inner :: object
-    r3 :: __main__.inner_f_obj_0
-    r4 :: bool
-    r5 :: object
-    r6 :: str
+    r2 :: __main__.inner_f_obj_0
+    r3 :: object
+    r4 :: str
 L0:
     r0 = f_env()
     if flag goto L1 else goto L2 :: bool
 L1:
     r1 = inner_f_obj()
-    r1.__mypyc_env__ = r0; r2 = is_error
+    r1.__mypyc_env__ = r0
     inner = r1
     goto L3
 L2:
-    r3 = inner_f_obj_0()
-    r3.__mypyc_env__ = r0; r4 = is_error
-    inner = r3
+    r2 = inner_f_obj_0()
+    r2.__mypyc_env__ = r0
+    inner = r2
 L3:
-    r5 = PyObject_Vectorcall(inner, 0, 0, 0)
-    r6 = cast(str, r5)
-    return r6
+    r3 = PyObject_Vectorcall(inner, 0, 0, 0)
+    r4 = cast(str, r3)
+    return r4
 
 [case testNestedFunctionsCallEachOther]
 from typing import Callable, List
@@ -691,43 +678,43 @@ def f(a):
     r0 :: __main__.f_env
     r1 :: bool
     r2 :: __main__.foo_f_obj
-    r3, r4 :: bool
-    r5 :: __main__.bar_f_obj
-    r6, r7 :: bool
-    r8 :: __main__.baz_f_obj
-    r9, r10 :: bool
-    r11, r12 :: object
-    r13, r14 :: int
-    r15, r16 :: object
-    r17 :: object[1]
-    r18 :: object_ptr
-    r19 :: object
-    r20, r21 :: int
+    r3 :: bool
+    r4 :: __main__.bar_f_obj
+    r5 :: bool
+    r6 :: __main__.baz_f_obj
+    r7 :: bool
+    r8, r9 :: object
+    r10, r11 :: int
+    r12, r13 :: object
+    r14 :: object[1]
+    r15 :: object_ptr
+    r16 :: object
+    r17, r18 :: int
 L0:
     r0 = f_env()
     r0.a = a; r1 = is_error
     r2 = foo_f_obj()
-    r2.__mypyc_env__ = r0; r3 = is_error
-    r0.foo = r2; r4 = is_error
-    r5 = bar_f_obj()
-    r5.__mypyc_env__ = r0; r6 = is_error
-    r0.bar = r5; r7 = is_error
-    r8 = baz_f_obj()
-    r8.__mypyc_env__ = r0; r9 = is_error
-    r0.baz = r8; r10 = is_error
-    r11 = r0.bar
-    r12 = PyObject_Vectorcall(r11, 0, 0, 0)
-    r13 = unbox(int, r12)
-    r14 = r0.a
-    r15 = r0.baz
-    r16 = box(int, r14)
-    r17 = [r16]
-    r18 = load_address r17
-    r19 = PyObject_Vectorcall(r15, r18, 1, 0)
-    keep_alive r16
-    r20 = unbox(int, r19)
-    r21 = CPyTagged_Add(r13, r20)
-    return r21
+    r2.__mypyc_env__ = r0
+    r0.foo = r2; r3 = is_error
+    r4 = bar_f_obj()
+    r4.__mypyc_env__ = r0
+    r0.bar = r4; r5 = is_error
+    r6 = baz_f_obj()
+    r6.__mypyc_env__ = r0
+    r0.baz = r6; r7 = is_error
+    r8 = r0.bar
+    r9 = PyObject_Vectorcall(r8, 0, 0, 0)
+    r10 = unbox(int, r9)
+    r11 = r0.a
+    r12 = r0.baz
+    r13 = box(int, r11)
+    r14 = [r13]
+    r15 = load_address r14
+    r16 = PyObject_Vectorcall(r12, r15, 1, 0)
+    keep_alive r13
+    r17 = unbox(int, r16)
+    r18 = CPyTagged_Add(r10, r17)
+    return r18
 
 [case testLambdas]
 def f(x: int, y: int) -> None:
@@ -791,30 +778,29 @@ def f(x, y):
     x, y :: int
     r0 :: __main__.f_env
     r1 :: __main__.__mypyc_lambda__0_f_obj
-    r2, r3 :: bool
-    r4 :: __main__.__mypyc_lambda__1_f_obj
-    r5 :: bool
-    t, r6, r7 :: object
-    r8 :: object[2]
-    r9 :: object_ptr
-    r10 :: object
-    r11 :: None
+    r2 :: bool
+    r3 :: __main__.__mypyc_lambda__1_f_obj
+    t, r4, r5 :: object
+    r6 :: object[2]
+    r7 :: object_ptr
+    r8 :: object
+    r9 :: None
 L0:
     r0 = f_env()
     r1 = __mypyc_lambda__0_f_obj()
-    r1.__mypyc_env__ = r0; r2 = is_error
-    r0.s = r1; r3 = is_error
-    r4 = __mypyc_lambda__1_f_obj()
-    r4.__mypyc_env__ = r0; r5 = is_error
-    t = r4
-    r6 = box(int, x)
-    r7 = box(int, y)
-    r8 = [r6, r7]
-    r9 = load_address r8
-    r10 = PyObject_Vectorcall(t, r9, 2, 0)
-    keep_alive r6, r7
-    r11 = unbox(None, r10)
-    return r11
+    r1.__mypyc_env__ = r0
+    r0.s = r1; r2 = is_error
+    r3 = __mypyc_lambda__1_f_obj()
+    r3.__mypyc_env__ = r0
+    t = r3
+    r4 = box(int, x)
+    r5 = box(int, y)
+    r6 = [r4, r5]
+    r7 = load_address r6
+    r8 = PyObject_Vectorcall(t, r7, 2, 0)
+    keep_alive r4, r5
+    r9 = unbox(None, r8)
+    return r9
 
 [case testRecursiveFunction]
 from typing import Callable
diff --git a/mypyc/test-data/run-functions.test b/mypyc/test-data/run-functions.test
index 8932d0f11006..3e1ee1379ca4 100644
--- a/mypyc/test-data/run-functions.test
+++ b/mypyc/test-data/run-functions.test
@@ -1346,6 +1346,26 @@ def test_nested() -> None:
 {'x': 1}
 1
 
+[case testNestedFunctionEnvironmentIsReadOnly]
+from typing import Any, Callable
+
+def outer(value: str) -> Callable[[], str]:
+    def inner() -> str:
+        return value
+    return inner
+
+def test_environment_link_is_read_only() -> None:
+    fn: Any = outer("value")
+    environment = fn.__mypyc_env__
+    try:
+        fn.__mypyc_env__ = None
+    except AttributeError:
+        pass
+    else:
+        assert False
+    assert fn.__mypyc_env__ is environment
+    assert fn() == "value"
+
 [case testFunctoolsUpdateWrapper]
 import functools