diff --git a/tokio/src/runtime/time/source.rs b/tokio/src/runtime/time/source.rs
index e371c207cdb..e3ba8d790c0 100644
--- a/tokio/src/runtime/time/source.rs
+++ b/tokio/src/runtime/time/source.rs
@@ -22,9 +22,11 @@ impl TimeSource {
     pub(crate) fn instant_to_tick(&self, t: Instant) -> u64 {
         // round up
         let dur: Duration = t.saturating_duration_since(self.start_time);
-        let ms = dur.as_millis();
-
-        ms.try_into().unwrap_or(MAX_SAFE_MILLIS_DURATION)
+        let ms = dur
+            .as_millis()
+            .try_into()
+            .unwrap_or(MAX_SAFE_MILLIS_DURATION);
+        ms.min(MAX_SAFE_MILLIS_DURATION)
     }
 
     pub(crate) fn tick_to_duration(&self, t: u64) -> Duration {
@@ -34,4 +36,10 @@ impl TimeSource {
     pub(crate) fn now(&self, clock: &Clock) -> u64 {
         self.instant_to_tick(clock.now())
     }
+
+    #[cfg(test)]
+    #[allow(dead_code)]
+    pub(super) fn start_time(&self) -> Instant {
+        self.start_time
+    }
 }
diff --git a/tokio/src/runtime/time/tests/mod.rs b/tokio/src/runtime/time/tests/mod.rs
index 676cf55f9c6..0e453433691 100644
--- a/tokio/src/runtime/time/tests/mod.rs
+++ b/tokio/src/runtime/time/tests/mod.rs
@@ -267,3 +267,17 @@ fn poll_process_levels_targeted() {
     handle.process_at_time(0, 192);
     handle.process_at_time(0, 192);
 }
+
+#[test]
+#[cfg(not(loom))]
+fn instant_to_tick_max() {
+    use crate::runtime::time::entry::MAX_SAFE_MILLIS_DURATION;
+
+    let rt = rt(true);
+    let handle = rt.handle().inner.driver().time();
+
+    let start_time = handle.time_source.start_time();
+    let long_future = start_time + std::time::Duration::from_millis(MAX_SAFE_MILLIS_DURATION + 1);
+
+    assert!(handle.time_source.instant_to_tick(long_future) <= MAX_SAFE_MILLIS_DURATION);
+}