diff --git a/lib/show_mem.c b/lib/show_mem.c
index 09225796991a..5e256271b47b 100644
--- a/lib/show_mem.c
+++ b/lib/show_mem.c
@@ -28,7 +28,7 @@ void show_mem(unsigned int filter)
 				continue;
 
 			total += zone->present_pages;
-			reserved = zone->present_pages - zone->managed_pages;
+			reserved += zone->present_pages - zone->managed_pages;
 
 			if (is_highmem_idx(zoneid))
 				highmem += zone->present_pages;