diff --git a/src/runtime/time.go b/src/runtime/time.go
index 4b179d84fcd..37c55b2b461 100644
--- a/src/runtime/time.go
+++ b/src/runtime/time.go
@@ -526,7 +526,17 @@ func (t *timer) needsAdd() bool {
 // may result in concurrent calls to t.maybeAdd,
 // so we cannot assume that t is not in a heap on entry to t.maybeAdd.
 func (t *timer) maybeAdd() {
-	ts := &getg().m.p.ptr().timers
+	// Note: Not holding any locks on entry to t.maybeAdd,
+	// so the current g can be rescheduled to a different M and P
+	// at any time, including between the ts := assignment and the
+	// call to ts.lock. If a reschedule happened then, we would be
+	// adding t to some other P's timers, perhaps even a P that the scheduler
+	// has marked as idle with no timers, in which case the timer could
+	// go unnoticed until long after t.when.
+	// Calling acquirem instead of using getg().m makes sure that
+	// we end up locking and inserting into the current P's timers.
+	mp := acquirem()
+	ts := &mp.p.ptr().timers
 	ts.lock()
 	ts.cleanHead()
 	t.lock()
@@ -539,6 +549,7 @@ func (t *timer) maybeAdd() {
 	}
 	t.unlock()
 	ts.unlock()
+	releasem(mp)
 	if when > 0 {
 		wakeNetPoller(when)
 	}
diff --git a/src/time/sleep_test.go b/src/time/sleep_test.go
index 565af16d4d7..8c28b1e4a92 100644
--- a/src/time/sleep_test.go
+++ b/src/time/sleep_test.go
@@ -656,6 +656,13 @@ func TestZeroTimer(t *testing.T) {
 	t.Run("impl=func", func(t *testing.T) {
 		testZeroTimer(t, newTimerFunc)
 	})
+	t.Run("impl=cache", func(t *testing.T) {
+		timer := newTimerFunc(Hour)
+		testZeroTimer(t, func(d Duration) *Timer {
+			timer.Reset(d)
+			return timer
+		})
+	})
 }
 
 func testZeroTimer(t *testing.T, newTimer func(Duration) *Timer) {