diff --git a/src/core/exec-invoke.c b/src/core/exec-invoke.c
index ff6d73b9db..20efad6912 100644
--- a/src/core/exec-invoke.c
+++ b/src/core/exec-invoke.c
@@ -2134,7 +2134,7 @@ static int build_environment(
         }
 
         if (!sd_id128_is_null(p->invocation_id)) {
-                assert(p->invocation_id_string);
+                assert(!isempty(p->invocation_id_string));
 
                 r = strv_extend_joined_with_size(&e, &n, "INVOCATION_ID=", p->invocation_id_string);
                 if (r < 0)