diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
index 0f6f3bc..63060a1 100644
--- a/drivers/acpi/osl.c
+++ b/drivers/acpi/osl.c
@@ -205,7 +205,7 @@
 {
 	if (phys > ULONG_MAX) {
 		printk(KERN_ERR PREFIX "Cannot map memory that high\n");
-		return 0;
+		return NULL;
 	}
 	if (acpi_gbl_permanent_mmap)
 		/*