diff --git a/src/notify/notify.c b/src/notify/notify.c
index cdca928f90..d17df1eafa 100644
--- a/src/notify/notify.c
+++ b/src/notify/notify.c
@@ -604,6 +604,7 @@ static int run(int argc, char* argv[]) {
         }
 
         our_env[i++] = NULL;
+        assert(i <= ELEMENTSOF(our_env));
 
         final_env = strv_env_merge((char**) our_env, arg_env);
         if (!final_env)