diff --git a/src/basic/time-util.c b/src/basic/time-util.c
index 06c465e0e40..1e042b8b600 100644
--- a/src/basic/time-util.c
+++ b/src/basic/time-util.c
@@ -1043,6 +1043,14 @@ int parse_timestamp(const char *t, usec_t *ret) {
         if (shared == MAP_FAILED)
                 return negative_errno();
 
+        /* The input string may be in argv. Let's copy it. */
+        _cleanup_free_ char *t_copy = strdup(t);
+        if (!t_copy)
+                return -ENOMEM;
+
+        t = t_copy;
+        assert_se(tz = endswith(t_copy, tz));
+
         r = safe_fork("(sd-timestamp)", FORK_RESET_SIGNALS|FORK_CLOSE_ALL_FDS|FORK_DEATHSIG_SIGKILL|FORK_WAIT, NULL);
         if (r < 0) {
                 (void) munmap(shared, sizeof *shared);