diff --git a/arch/um/kernel/physmem.c b/arch/um/kernel/physmem.c
index e7c7b53a1435..87b51089b061 100644
--- a/arch/um/kernel/physmem.c
+++ b/arch/um/kernel/physmem.c
@@ -80,10 +80,10 @@ void __init setup_physmem(unsigned long start, unsigned long reserve_end,
 			  unsigned long len, unsigned long long highmem)
 {
 	unsigned long reserve = reserve_end - start;
-	long map_size = len - reserve;
+	unsigned long map_size = len - reserve;
 	int err;
 
-	if(map_size <= 0) {
+	if (len <= reserve) {
 		os_warn("Too few physical memory! Needed=%lu, given=%lu\n",
 			reserve, len);
 		exit(1);
@@ -94,7 +94,7 @@ void __init setup_physmem(unsigned long start, unsigned long reserve_end,
 	err = os_map_memory((void *) reserve_end, physmem_fd, reserve,
 			    map_size, 1, 1, 1);
 	if (err < 0) {
-		os_warn("setup_physmem - mapping %ld bytes of memory at 0x%p "
+		os_warn("setup_physmem - mapping %lu bytes of memory at 0x%p "
 			"failed - errno = %d\n", map_size,
 			(void *) reserve_end, err);
 		exit(1);