diff --git a/src/stralloc.c b/src/stralloc.c
index aa3af8f3f69d29d0e28cf97ca2fe0ea3ba15368e..ddfe9635d0967c7aca47c352cce2c04fa7ec936f 100644
--- a/src/stralloc.c
+++ b/src/stralloc.c
@@ -233,7 +233,7 @@ static INLINE int find_magnitude2(const p_wchar2 *s, ptrdiff_t len)
 
 static INLINE unsigned min_magnitude(const unsigned c)
 {
-  return c<256 ? 0 : c<65536 ? 1 : 2;
+  return LIKELY(c<256) ? 0 : LIKELY(c<65536) ? 1 : 2;
 }
 
 void low_set_index(struct pike_string *s, ptrdiff_t pos, int value)