diff --git a/Include/internal/pycore_pystate.h b/Include/internal/pycore_pystate.h
index d96ba312070..7ac4ad5869b 100644
--- a/Include/internal/pycore_pystate.h
+++ b/Include/internal/pycore_pystate.h
@@ -86,6 +86,21 @@ _PyThreadState_GET(void)
 #undef PyThreadState_GET
 #define PyThreadState_GET() _PyThreadState_GET()
 
+PyAPI_FUNC(void) _Py_NO_RETURN _Py_FatalError_TstateNULL(const char *func);
+
+static inline void
+_Py_EnsureFuncTstateNotNULL(const char *func, PyThreadState *tstate)
+{
+    if (tstate == NULL) {
+        _Py_FatalError_TstateNULL(func);
+    }
+}
+
+// Call Py_FatalError() if tstate is NULL
+#define _Py_EnsureTstateNotNULL(tstate) \
+    _Py_EnsureFuncTstateNotNULL(__func__, tstate)
+
+
 /* Get the current interpreter state.
 
    The macro is unsafe: it does not check for error and it can return NULL.
@@ -96,7 +111,9 @@ _PyThreadState_GET(void)
    and _PyGILState_GetInterpreterStateUnsafe(). */
 static inline PyInterpreterState* _PyInterpreterState_GET(void) {
     PyThreadState *tstate = _PyThreadState_GET();
-    assert(tstate != NULL);
+#ifdef Py_DEBUG
+    _Py_EnsureTstateNotNULL(tstate);
+#endif
     return tstate->interp;
 }
 
diff --git a/Lib/test/test_capi.py b/Lib/test/test_capi.py
index 44693b8fdd7..5b8b9f6a86f 100644
--- a/Lib/test/test_capi.py
+++ b/Lib/test/test_capi.py
@@ -68,7 +68,10 @@ class CAPITest(unittest.TestCase):
         self.assertTrue(err.rstrip().startswith(
                          b'Fatal Python error: '
                          b'PyThreadState_Get: '
-                         b'current thread state is NULL (released GIL?)'))
+                         b'the function must be called with the GIL held, '
+                         b'but the GIL is released '
+                         b'(the current Python thread state is NULL)'),
+                        err)
 
     def test_memoryview_from_NULL_pointer(self):
         self.assertRaises(ValueError, _testcapi.make_memoryview_from_NULL_pointer)
diff --git a/Python/ceval.c b/Python/ceval.c
index a79773f8511..01dd361e503 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -240,16 +240,15 @@ UNSIGNAL_ASYNC_EXC(PyInterpreterState *interp)
 #endif
 #include "ceval_gil.h"
 
-static void
-ensure_tstate_not_null(const char *func, PyThreadState *tstate)
+void _Py_NO_RETURN
+_Py_FatalError_TstateNULL(const char *func)
 {
-    if (tstate == NULL) {
-        _Py_FatalErrorFunc(func,
-                           "current thread state is NULL (released GIL?)");
-    }
+    _Py_FatalErrorFunc(func,
+                       "the function must be called with the GIL held, "
+                       "but the GIL is released "
+                       "(the current Python thread state is NULL)");
 }
 
-
 #ifdef EXPERIMENTAL_ISOLATED_SUBINTERPRETERS
 int
 _PyEval_ThreadsInitialized(PyInterpreterState *interp)
@@ -374,7 +373,7 @@ PyEval_AcquireLock(void)
 {
     _PyRuntimeState *runtime = &_PyRuntime;
     PyThreadState *tstate = _PyRuntimeState_GetThreadState(runtime);
-    ensure_tstate_not_null(__func__, tstate);
+    _Py_EnsureTstateNotNULL(tstate);
 
     take_gil(tstate);
 }
@@ -403,7 +402,7 @@ _PyEval_ReleaseLock(PyThreadState *tstate)
 void
 PyEval_AcquireThread(PyThreadState *tstate)
 {
-    ensure_tstate_not_null(__func__, tstate);
+    _Py_EnsureTstateNotNULL(tstate);
 
     take_gil(tstate);
 
@@ -442,7 +441,7 @@ void
 _PyEval_ReInitThreads(_PyRuntimeState *runtime)
 {
     PyThreadState *tstate = _PyRuntimeState_GetThreadState(runtime);
-    ensure_tstate_not_null(__func__, tstate);
+    _Py_EnsureTstateNotNULL(tstate);
 
 #ifdef EXPERIMENTAL_ISOLATED_SUBINTERPRETERS
     struct _gil_runtime_state *gil = &tstate->interp->ceval.gil;
@@ -486,7 +485,7 @@ PyEval_SaveThread(void)
 #else
     PyThreadState *tstate = _PyThreadState_Swap(&runtime->gilstate, NULL);
 #endif
-    ensure_tstate_not_null(__func__, tstate);
+    _Py_EnsureTstateNotNULL(tstate);
 
     struct _ceval_runtime_state *ceval = &runtime->ceval;
     struct _ceval_state *ceval2 = &tstate->interp->ceval;
@@ -502,7 +501,7 @@ PyEval_SaveThread(void)
 void
 PyEval_RestoreThread(PyThreadState *tstate)
 {
-    ensure_tstate_not_null(__func__, tstate);
+    _Py_EnsureTstateNotNULL(tstate);
 
     take_gil(tstate);
 
@@ -944,7 +943,7 @@ eval_frame_handle_pending(PyThreadState *tstate)
 PyObject* _Py_HOT_FUNCTION
 _PyEval_EvalFrameDefault(PyThreadState *tstate, PyFrameObject *f, int throwflag)
 {
-    ensure_tstate_not_null(__func__, tstate);
+    _Py_EnsureTstateNotNULL(tstate);
 
 #ifdef DXPAIRS
     int lastopcode = 0;
diff --git a/Python/errors.c b/Python/errors.c
index 70365aaca58..5d1725679c4 100644
--- a/Python/errors.c
+++ b/Python/errors.c
@@ -1426,7 +1426,7 @@ void
 _PyErr_WriteUnraisableMsg(const char *err_msg_str, PyObject *obj)
 {
     PyThreadState *tstate = _PyThreadState_GET();
-    assert(tstate != NULL);
+    _Py_EnsureTstateNotNULL(tstate);
 
     PyObject *err_msg = NULL;
     PyObject *exc_type, *exc_value, *exc_tb;
diff --git a/Python/pystate.c b/Python/pystate.c
index 119fe31a84b..f92c55e7471 100644
--- a/Python/pystate.c
+++ b/Python/pystate.c
@@ -39,16 +39,6 @@ extern "C" {
     _Py_atomic_store_relaxed(&(gilstate)->tstate_current, \
                              (uintptr_t)(value))
 
-static void
-ensure_tstate_not_null(const char *func, PyThreadState *tstate)
-{
-    if (tstate == NULL) {
-        _Py_FatalErrorFunc(func,
-                           "current thread state is NULL (released GIL?)");
-    }
-}
-
-
 /* Forward declarations */
 static PyThreadState *_PyGILState_GetThisThreadState(struct _gilstate_runtime_state *gilstate);
 static void _PyThreadState_Delete(PyThreadState *tstate, int check_current);
@@ -431,7 +421,7 @@ PyInterpreterState *
 PyInterpreterState_Get(void)
 {
     PyThreadState *tstate = _PyThreadState_GET();
-    ensure_tstate_not_null(__func__, tstate);
+    _Py_EnsureTstateNotNULL(tstate);
     PyInterpreterState *interp = tstate->interp;
     if (interp == NULL) {
         Py_FatalError("no current interpreter");
@@ -846,7 +836,7 @@ static void
 tstate_delete_common(PyThreadState *tstate,
                      struct _gilstate_runtime_state *gilstate)
 {
-    ensure_tstate_not_null(__func__, tstate);
+    _Py_EnsureTstateNotNULL(tstate);
     PyInterpreterState *interp = tstate->interp;
     if (interp == NULL) {
         Py_FatalError("NULL interpreter");
@@ -897,7 +887,7 @@ PyThreadState_Delete(PyThreadState *tstate)
 void
 _PyThreadState_DeleteCurrent(PyThreadState *tstate)
 {
-    ensure_tstate_not_null(__func__, tstate);
+    _Py_EnsureTstateNotNULL(tstate);
     struct _gilstate_runtime_state *gilstate = &tstate->interp->runtime->gilstate;
     tstate_delete_common(tstate, gilstate);
     _PyRuntimeGILState_SetThreadState(gilstate, NULL);
@@ -975,7 +965,7 @@ PyThreadState *
 PyThreadState_Get(void)
 {
     PyThreadState *tstate = _PyThreadState_GET();
-    ensure_tstate_not_null(__func__, tstate);
+    _Py_EnsureTstateNotNULL(tstate);
     return tstate;
 }
 
diff --git a/Python/sysmodule.c b/Python/sysmodule.c
index 914beb7e127..e3fe1436145 100644
--- a/Python/sysmodule.c
+++ b/Python/sysmodule.c
@@ -457,7 +457,7 @@ static PyObject *
 sys_audit(PyObject *self, PyObject *const *args, Py_ssize_t argc)
 {
     PyThreadState *tstate = _PyThreadState_GET();
-    assert(tstate != NULL);
+    _Py_EnsureTstateNotNULL(tstate);
 
     if (argc == 0) {
         _PyErr_SetString(tstate, PyExc_TypeError,