diff --git a/mono/utils/mono-threads.c b/mono/utils/mono-threads.c
index bf73e01c79704..97dca50312e12 100644
--- a/mono/utils/mono-threads.c
+++ b/mono/utils/mono-threads.c
@@ -586,6 +586,7 @@ unregister_thread (void *arg)
 	mono_thread_hazardous_try_free (info, free_thread_info);
 
 	mono_thread_small_id_free (small_id);
+	mono_native_tls_set_value (small_id_key, NULL);
 
 	mono_threads_signal_thread_handle (handle);