diff --git a/sys/libkern/memmem.c b/sys/libkern/memmem.c
index 9c6e0d162eb1..11c3d9eec508 100644
--- a/sys/libkern/memmem.c
+++ b/sys/libkern/memmem.c
@@ -52,9 +52,9 @@ memmem(const void *l, size_t l_len, const void *s, size_t s_len)
                 return memchr(l, (int)*cs, l_len);
 
         /* the last position where its possible to find "s" in "l" */
-        last = (char *)cl + l_len - s_len;
+        last = __DECONST(char *, cl) + l_len - s_len;
 
-        for (cur = (char *)cl; cur <= last; cur++)
+        for (cur = __DECONST(char *, cl); cur <= last; cur++)
                 if (cur[0] == cs[0] && memcmp(cur, cs, s_len) == 0)
                         return cur;