diff --git a/src/core/timer.c b/src/core/timer.c
index 701949fd60..3032a237b1 100644
--- a/src/core/timer.c
+++ b/src/core/timer.c
@@ -614,9 +614,23 @@ static int timer_start(Unit *u) {
         if (t->stamp_path) {
                 struct stat st;
 
-                if (stat(t->stamp_path, &st) >= 0)
-                        t->last_trigger.realtime = timespec_load(&st.st_atim);
-                else if (errno == ENOENT)
+                if (stat(t->stamp_path, &st) >= 0) {
+                        usec_t ft;
+
+                        /* Load the file timestamp, but only if it is actually in the past. If it is in the future,
+                         * something is wrong with the system clock. */
+
+                        ft = timespec_load(&st.st_mtim);
+                        if (ft < now(CLOCK_REALTIME))
+                                t->last_trigger.realtime = ft;
+                        else {
+                                char z[FORMAT_TIMESTAMP_MAX];
+
+                                log_unit_warning(u, "Not using persistent file timestamp %s as it is in the future.",
+                                                 format_timestamp(z, sizeof(z), ft));
+                        }
+
+                } else if (errno == ENOENT)
                         /* The timer has never run before,
                          * make sure a stamp file exists.
                          */