diff --git a/src/basic/cgroup-util.h b/src/basic/cgroup-util.h
index 546b86eb7c..c2bf487ab3 100644
--- a/src/basic/cgroup-util.h
+++ b/src/basic/cgroup-util.h
@@ -36,7 +36,7 @@ typedef enum CGroupController {
         _CGROUP_CONTROLLER_INVALID = -1,
 } CGroupController;
 
-#define CGROUP_CONTROLLER_TO_MASK(c) (1 << (c))
+#define CGROUP_CONTROLLER_TO_MASK(c) (1U << (c))
 
 /* A bit mask of well known cgroup controllers */
 typedef enum CGroupMask {