diff --git a/class.c b/class.c
index b1bd896996..f5090d7f0f 100644
--- a/class.c
+++ b/class.c
@@ -29,7 +29,6 @@
 #include "internal/variable.h"
 #include "ruby/st.h"
 #include "vm_core.h"
-#include "gc.h"
 
 #define id_attached id__attached__
 
diff --git a/gc.h b/gc.h
index 1ae7733e53..91d6e5787d 100644
--- a/gc.h
+++ b/gc.h
@@ -127,7 +127,6 @@ void rb_objspace_reachable_objects_from_root(void (func)(const char *category, V
 int rb_objspace_markable_object_p(VALUE obj);
 int rb_objspace_internal_object_p(VALUE obj);
 int rb_objspace_marked_object_p(VALUE obj);
-int rb_objspace_garbage_object_p(VALUE obj);
 
 void rb_objspace_each_objects(
     int (*callback)(void *start, void *end, size_t stride, void *data),
diff --git a/internal/gc.h b/internal/gc.h
index 49b12db2df..b7b29214cf 100644
--- a/internal/gc.h
+++ b/internal/gc.h
@@ -99,6 +99,7 @@ VALUE rb_class_allocate_instance(VALUE klass);
 void rb_gc_ractor_newobj_cache_clear(rb_ractor_newobj_cache_t *newobj_cache);
 size_t rb_gc_obj_slot_size(VALUE obj);
 bool rb_gc_size_allocatable_p(size_t size);
+int rb_objspace_garbage_object_p(VALUE obj);
 
 RUBY_SYMBOL_EXPORT_BEGIN
 /* gc.c (export) */