diff --git a/kernel/resource.c b/kernel/resource.c
index 74af2d7..f5b518e 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -490,7 +490,7 @@
 {
 	switch (res->flags & (IORESOURCE_SIZEALIGN | IORESOURCE_STARTALIGN)) {
 	case IORESOURCE_SIZEALIGN:
-		return res->end - res->start + 1;
+		return resource_size(res);
 	case IORESOURCE_STARTALIGN:
 		return res->start;
 	default: