diff --git a/include/string.h b/include/string.h
index 1cfc1e04e56..f000a87e1c7 100644
--- a/include/string.h
+++ b/include/string.h
@@ -100,10 +100,10 @@ FAR void  *memrchr(FAR const void *s, int c, size_t n);
 FAR void  *rawmemchr(FAR const void *s, int c);
 FAR void  *memccpy(FAR void *s1, FAR const void *s2, int c, size_t n);
 int        memcmp(FAR const void *s1, FAR const void *s2, size_t n);
-FAR void  *memcpy(FAR void *dest, FAR const void *src, size_t n);
+FAR void  *memcpy(FAR void *dest, FAR const void *src, size_t n) used_code;
 FAR void  *mempcpy(FAR void *dest, FAR const void *src, size_t n);
 FAR void  *memmove(FAR void *dest, FAR const void *src, size_t count);
-FAR void  *memset(FAR void *s, int c, size_t n);
+FAR void  *memset(FAR void *s, int c, size_t n) used_code;
 FAR void  *memmem(FAR const void *haystack, size_t haystacklen,
                   FAR const void *needle, size_t needlelen);