diff --git a/src/basic/time-util.c b/src/basic/time-util.c
index fd86f1d449..4ced1bc6a1 100644
--- a/src/basic/time-util.c
+++ b/src/basic/time-util.c
@@ -844,6 +844,8 @@ from_tm:
                 return -EINVAL;
 
 finish:
+        if (ret + plus < ret) /* overflow? */
+                return -EINVAL;
         ret += plus;
         if (ret > USEC_TIMESTAMP_FORMATTABLE_MAX)
                 return -EINVAL;