diff --git a/lib/roken/mergesort_r.c b/lib/roken/mergesort_r.c
index 2d551a607..39b0301c4 100644
--- a/lib/roken/mergesort_r.c
+++ b/lib/roken/mergesort_r.c
@@ -85,7 +85,7 @@ static void insertionsort(u_char *, size_t, size_t, cmp_t, void *);
  */
 /* Assumption: PSIZE is a power of 2. */
 #define EVAL(p) (u_char **)						\
-	((((u_char *)p + PSIZE - 1 - (u_char *) 0) & ~(PSIZE - 1)))
+	((((uintptr_t)p + PSIZE - 1) & ~(PSIZE - 1)))
 
 /*
  * Arguments are as for qsort_r, except thunk is moved to the last
@@ -114,7 +114,7 @@ mergesort_r(void *base, size_t nmemb, size_t size, cmp_t cmp, void *thunk)
 	 * Stupid subtraction for the Cray.
 	 */
 	iflag = 0;
-	if (!(size % ISIZE) && !(((char *)base - (char *)0) % ISIZE))
+	if (!(size % ISIZE) && !(((uintptr_t)base) % ISIZE))
 		iflag = 1;
 
 	if ((list2 = malloc(nmemb * size + PSIZE)) == NULL)