diff --git a/thread_sync.c b/thread_sync.c
index efa6208f5d..d7975beeff 100644
--- a/thread_sync.c
+++ b/thread_sync.c
@@ -1227,6 +1227,12 @@ undumpable(VALUE obj)
     UNREACHABLE;
 }
 
+static void
+alias_global_const(const char *name, VALUE klass)
+{
+    rb_define_const(rb_cObject, name, klass);
+}
+
 static void
 Init_thread_sync(void)
 {
@@ -1309,7 +1315,7 @@ Init_thread_sync(void)
     rb_define_method(rb_cConditionVariable, "broadcast", rb_condvar_broadcast, 0);
 
 #define ALIAS_GLOBAL_CONST(name) \
-    rb_define_const(rb_cObject, #name, rb_c##name)
+    alias_global_const(#name, rb_c##name)
 
     ALIAS_GLOBAL_CONST(Mutex);
     ALIAS_GLOBAL_CONST(Queue);