diff --git a/thread.c b/thread.c
index 342d4fe..86df518 100644
--- a/thread.c
+++ b/thread.c
@@ -563,6 +563,8 @@ thread_create_core(VALUE thval, VALUE args, VALUE (*fn)(ANYARGS))
     th->priority = GET_THREAD()->priority;
     th->thgroup = GET_THREAD()->thgroup;
 
+    th->spinlock_waiting_gvl = 0;
+
     native_mutex_initialize(&th->interrupt_lock);
     if (GET_VM()->event_hooks != NULL)
 	th->event_flags |= RUBY_EVENT_VM;
@@ -3573,9 +3575,11 @@ rb_mutex_lock(VALUE self)
 	    }
 	    GVL_UNLOCK_BEGIN();
 	    interrupted = lock_func(th, mutex, timeout_ms);
+	    th->spinlock_waiting_gvl = 1;
 	    native_mutex_unlock(&mutex->lock);
 	    GVL_UNLOCK_END();
 
+	    th->spinlock_waiting_gvl = 0;
 	    reset_unblock_function(th, &oldubf);
 
 	    th->locking_mutex = Qfalse;
@@ -4740,7 +4744,7 @@ check_deadlock_i(st_data_t key, st_data_t val, int *found)
 	GetMutexPtr(th->locking_mutex, mutex);
 
 	native_mutex_lock(&mutex->lock);
-	if (mutex->th == th || (!mutex->th && mutex->cond_waiting)) {
+	if (mutex->th == th || (!mutex->th && (mutex->cond_waiting || th->spinlock_waiting_gvl))) {
 	    *found = 1;
 	}
 	native_mutex_unlock(&mutex->lock);
diff --git a/vm_core.h b/vm_core.h
index 7211005..849482d 100644
--- a/vm_core.h
+++ b/vm_core.h
@@ -440,6 +440,7 @@ typedef struct rb_thread_struct {
     rb_thread_lock_t interrupt_lock;
     struct rb_unblock_callback unblock;
     VALUE locking_mutex;
+    int spinlock_waiting_gvl;
     struct rb_mutex_struct *keeping_mutexes;
 
     struct rb_vm_tag *tag;