diff --git a/mm/slab.c b/mm/slab.c
index 437d338..cf19ff2 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -308,12 +308,12 @@
 #define	SIZE_L3 (1 + MAX_NUMNODES)
 
 /*
- * This function may be completely optimized away if
+ * This function must be completely optimized away if
  * a constant is passed to it. Mostly the same as
  * what is in linux/slab.h except it returns an
  * index.
  */
-static inline int index_of(const size_t size)
+static __always_inline int index_of(const size_t size)
 {
 	if (__builtin_constant_p(size)) {
 		int i = 0;
@@ -329,7 +329,8 @@
 			extern void __bad_size(void);
 			__bad_size();
 		}
-	}
+	} else
+		BUG();
 	return 0;
 }