diff --git a/pmap.c b/pmap.c
index 17e0e304..ac45f5bb 100644
--- a/pmap.c
+++ b/pmap.c
@@ -518,7 +518,7 @@ static int one_proc(proc_t * p)
 	unsigned long total_shared = 0ul;
 	unsigned long total_private_readonly = 0ul;
 	unsigned long total_private_writeable = 0ul;
-	KLONG diff = 0;
+	unsigned KLONG diff = 0;
 	const char *cp2 = NULL;
 	unsigned long long rss = 0ull;
 	unsigned long long private_dirty = 0ull;