diff --git a/include/mruby/string.h b/include/mruby/string.h
index 91454f37d..4999c7308 100644
--- a/include/mruby/string.h
+++ b/include/mruby/string.h
@@ -48,8 +48,8 @@ struct RStringEmbed {
 #define MRB_STR_TYPE_MASK 15
 
 #define MRB_STR_EMBED_LEN_SHIFT 6
-#define MRB_STR_EMBED_LEN_BIT 5
-#define MRB_STR_EMBED_LEN_MASK (((1 << MRB_STR_EMBED_LEN_BIT) - 1) << MRB_STR_EMBED_LEN_SHIFT)
+#define MRB_STR_EMBED_LEN_BITS 5
+#define MRB_STR_EMBED_LEN_MASK (((1 << MRB_STR_EMBED_LEN_BITS) - 1) << MRB_STR_EMBED_LEN_SHIFT)
 
 #define MRB_STR_BINARY    16
 #define MRB_STR_SINGLE_BYTE 32
diff --git a/src/string.c b/src/string.c
index 2f29449db..bb9402355 100644
--- a/src/string.c
+++ b/src/string.c
@@ -3187,7 +3187,7 @@ mrb_init_string(mrb_state *mrb)
 {
   struct RClass *s;
 
-  mrb_static_assert(RSTRING_EMBED_LEN_MAX < (1 << MRB_STR_EMBED_LEN_BIT),
+  mrb_static_assert(RSTRING_EMBED_LEN_MAX < (1 << MRB_STR_EMBED_LEN_BITS),
                     "pointer size too big for embedded string");
 
   mrb->string_class = s = mrb_define_class_id(mrb, MRB_SYM(String), mrb->object_class);             /* 15.2.10 */