diff --git a/Python/pylifecycle.c b/Python/pylifecycle.c
index 751c4d6d1d..6719fa22b3 100644
--- a/Python/pylifecycle.c
+++ b/Python/pylifecycle.c
@@ -1289,6 +1289,10 @@ Py_FinalizeEx(void)
     }
 #endif /* Py_TRACE_REFS */
 
+    if (tstate != interp->tstate_head || tstate->next != NULL) {
+        Py_FatalError("Py_EndInterpreter: not the last thread");
+    }
+
     /* Clear interpreter state and all thread states. */
     PyInterpreterState_Clear(interp);