diff --git a/library/common.h b/library/common.h
index 4f4c222fa6..3e81e81ea1 100644
--- a/library/common.h
+++ b/library/common.h
@@ -318,15 +318,15 @@ static inline void mbedtls_xor_no_simd(unsigned char *r,
 #define MBEDTLS_UNLIKELY(x)     x
 #endif
 
-#if defined(__has_builtin)
-#if __has_builtin(__builtin_assume)
 /* MBEDTLS_ASSUME may be used to provide additional information to the compiler
  * which can result in smaller code-size. */
+#if defined(__has_builtin)
+#if __has_builtin(__builtin_assume)
+/* clang provides __builtin_assume */
 #define MBEDTLS_ASSUME(x)       __builtin_assume(x)
-// clang provides __builtin_assume
 #elif __has_builtin(__builtin_unreachable)
+/* gcc can use __builtin_unreachable */
 #define MBEDTLS_ASSUME(x)       do { if (!(x)) __builtin_unreachable(); } while (0)
-// For gcc, use __builtin_unreachable
 #endif
 #endif
 #if !defined(MBEDTLS_ASSUME)