diff --git a/src/gc.c b/src/gc.c
index 3543bb76b..87ece69fa 100644
--- a/src/gc.c
+++ b/src/gc.c
@@ -1576,15 +1576,15 @@ mrb_init_gc(mrb_state *mrb)
 
   mrb_static_assert_object_size(RVALUE);
 
-  gc = mrb_define_module(mrb, "GC");
+  gc = mrb_define_module_id(mrb, MRB_SYM(GC));
 
-  mrb_define_class_method(mrb, gc, "start", gc_start, MRB_ARGS_NONE());
-  mrb_define_class_method(mrb, gc, "enable", gc_enable, MRB_ARGS_NONE());
-  mrb_define_class_method(mrb, gc, "disable", gc_disable, MRB_ARGS_NONE());
-  mrb_define_class_method(mrb, gc, "interval_ratio", gc_interval_ratio_get, MRB_ARGS_NONE());
-  mrb_define_class_method(mrb, gc, "interval_ratio=", gc_interval_ratio_set, MRB_ARGS_REQ(1));
-  mrb_define_class_method(mrb, gc, "step_ratio", gc_step_ratio_get, MRB_ARGS_NONE());
-  mrb_define_class_method(mrb, gc, "step_ratio=", gc_step_ratio_set, MRB_ARGS_REQ(1));
-  mrb_define_class_method(mrb, gc, "generational_mode=", gc_generational_mode_set, MRB_ARGS_REQ(1));
-  mrb_define_class_method(mrb, gc, "generational_mode", gc_generational_mode_get, MRB_ARGS_NONE());
+  mrb_define_class_method_id(mrb, gc, MRB_SYM(start), gc_start, MRB_ARGS_NONE());
+  mrb_define_class_method_id(mrb, gc, MRB_SYM(enable), gc_enable, MRB_ARGS_NONE());
+  mrb_define_class_method_id(mrb, gc, MRB_SYM(disable), gc_disable, MRB_ARGS_NONE());
+  mrb_define_class_method_id(mrb, gc, MRB_SYM(interval_ratio), gc_interval_ratio_get, MRB_ARGS_NONE());
+  mrb_define_class_method_id(mrb, gc, MRB_SYM_E(interval_ratio), gc_interval_ratio_set, MRB_ARGS_REQ(1));
+  mrb_define_class_method_id(mrb, gc, MRB_SYM(step_ratio), gc_step_ratio_get, MRB_ARGS_NONE());
+  mrb_define_class_method_id(mrb, gc, MRB_SYM_E(step_ratio), gc_step_ratio_set, MRB_ARGS_REQ(1));
+  mrb_define_class_method_id(mrb, gc, MRB_SYM_E(generational_mode), gc_generational_mode_set, MRB_ARGS_REQ(1));
+  mrb_define_class_method_id(mrb, gc, MRB_SYM(generational_mode), gc_generational_mode_get, MRB_ARGS_NONE());
 }