diff --git a/test/-ext-/symbol/test_inadvertent_creation.rb b/test/-ext-/symbol/test_inadvertent_creation.rb
index 40b3f59f7f..b0508e9a07 100644
--- a/test/-ext-/symbol/test_inadvertent_creation.rb
+++ b/test/-ext-/symbol/test_inadvertent_creation.rb
@@ -255,7 +255,7 @@ module Test_Symbol
       Thread.current.thread_variable_set(:test, nil)
       name = noninterned_name
       assert_not_send([Thread.current, :thread_variable?, name])
-      assert_not_interned(name)
+      assert_not_pinneddown(name)
     end
 
     def test_enumerable_inject_op
diff --git a/thread.c b/thread.c
index 13fef6be9a..91a953b9ab 100644
--- a/thread.c
+++ b/thread.c
@@ -3468,7 +3468,7 @@ rb_thread_variable_get(VALUE thread, VALUE key)
  */
 
 static VALUE
-rb_thread_variable_set(VALUE thread, VALUE id, VALUE val)
+rb_thread_variable_set(VALUE thread, VALUE key, VALUE val)
 {
     VALUE locals;
 
@@ -3477,7 +3477,7 @@ rb_thread_variable_set(VALUE thread, VALUE id, VALUE val)
     }
 
     locals = rb_thread_local_storage(thread);
-    return rb_hash_aset(locals, rb_to_symbol(id), val);
+    return rb_hash_aset(locals, rb_to_symbol(key), val);
 }
 
 /*
@@ -3667,16 +3667,13 @@ static VALUE
 rb_thread_variable_p(VALUE thread, VALUE key)
 {
     VALUE locals;
-    ID id = rb_check_id(&key);
-
-    if (!id) return Qfalse;
 
     if (LIKELY(!THREAD_LOCAL_STORAGE_INITIALISED_P(thread))) {
         return Qfalse;
     }
     locals = rb_thread_local_storage(thread);
 
-    if (rb_hash_lookup(locals, ID2SYM(id)) != Qnil) {
+    if (rb_hash_lookup(locals, rb_to_symbol(key)) != Qnil) {
         return Qtrue;
     }
     else {