diff --git a/src/libusbmuxd.c b/src/libusbmuxd.c
index 712c362..379a948 100644
--- a/src/libusbmuxd.c
+++ b/src/libusbmuxd.c
@@ -535,11 +535,11 @@
 	size_t r = fread(tmpbuf, 1, 512, f);
 	if (r > 0) {
 		char *p = tmpbuf;
-		while ((p-tmpbuf < r) && (*p != '(') && (*p != '\0')) p++;
+		while ((p-tmpbuf < (ssize_t)r) && (*p != '(') && (*p != '\0')) p++;
 		if (*p == '(') {
 			p++;
 			char *pname = p;
-			while ((p-tmpbuf < r) && (*p != ')') && (*p != '\0')) p++;
+			while ((p-tmpbuf < (ssize_t)r) && (*p != ')') && (*p != '\0')) p++;
 			if (*p == ')') {
 				*p = '\0';
 				prog_name = strdup(pname);