diff --git a/drivers/watchdog/pnx4008_wdt.c b/drivers/watchdog/pnx4008_wdt.c
index 4d227b15..430a584 100644
--- a/drivers/watchdog/pnx4008_wdt.c
+++ b/drivers/watchdog/pnx4008_wdt.c
@@ -264,7 +264,7 @@
 		return -ENOENT;
 	}
 
-	size = res->end - res->start + 1;
+	size = resource_size(res);
 	wdt_mem = request_mem_region(res->start, size, pdev->name);
 
 	if (wdt_mem == NULL) {