diff --git a/gc.c b/gc.c
index bd1483a1de..6ce83469e6 100644
--- a/gc.c
+++ b/gc.c
@@ -543,7 +543,7 @@ rb_objspace_free(rb_objspace_t *objspace)
 #define REQUIRED_SIZE_BY_MALLOC (sizeof(size_t) * 5)
 #define HEAP_SIZE (HEAP_ALIGN - REQUIRED_SIZE_BY_MALLOC)
 
-#define HEAP_OBJ_LIMIT (HEAP_SIZE/(unsigned int)sizeof(struct RVALUE) - (unsigned int)(sizeof(struct heaps_slot)/sizeof(struct RVALUE)+1))
+#define HEAP_OBJ_LIMIT (unsigned int)(HEAP_SIZE/sizeof(struct RVALUE) - (sizeof(struct heaps_slot)/sizeof(struct RVALUE)+1))
 #define HEAP_BITMAP_LIMIT (HEAP_OBJ_LIMIT/sizeof(uintptr_t)+1)
 
 #define GET_HEAP_HEADER(x) (HEAP_HEADER(((uintptr_t)x) & ~(HEAP_ALIGN_MASK)))