diff --git a/class.c b/class.c
index 7ac7813f17..8677a26d2f 100644
--- a/class.c
+++ b/class.c
@@ -465,7 +465,7 @@ static bool ensure_origin(VALUE klass);
 /**
  * If this flag is set, that module is allocated but not initialized yet.
  */
-enum {RMODULE_ALLOCATED_BUT_NOT_INITIALIZED = RUBY_FL_USER5};
+enum {RMODULE_ALLOCATED_BUT_NOT_INITIALIZED = RUBY_FL_USER1};
 
 static inline bool
 RMODULE_UNINITIALIZED(VALUE module)