diff --git a/config/os/gnu-linux/time.c b/config/os/gnu-linux/time.c
index 883b233..0fc6ae6 100644
--- a/config/os/gnu-linux/time.c
+++ b/config/os/gnu-linux/time.c
@@ -60,7 +60,7 @@ jack_hpet_init ()
 
 	hpet_ptr = (unsigned char *) mmap(NULL, HPET_MMAP_SIZE,
 					  PROT_READ, MAP_SHARED, hpet_fd, 0);
-	if (hpet_ptr == NULL) {
+	if (hpet_ptr == MAP_FAILED) {
 		jack_error ("This system has no mappable HPET device (%s)", strerror (errno));
 		close (hpet_fd);
 		return -1;