diff --git a/src/basic/cgroup-util.c b/src/basic/cgroup-util.c
index b33acf8df1..e65ad678ab 100644
--- a/src/basic/cgroup-util.c
+++ b/src/basic/cgroup-util.c
@@ -1245,7 +1245,7 @@ static const char *skip_session(const char *p) {
                  * here. */
 
                 if (!session_id_valid(buf))
-                        return false;
+                        return NULL;
 
                 p += n;
                 p += strspn(p, "/");