diff --git a/logging/logging_test.go b/logging/logging_test.go
index d3e15b155d7f..1f07c7ba7f83 100644
--- a/logging/logging_test.go
+++ b/logging/logging_test.go
@@ -1420,7 +1420,7 @@ func TestInstrumentationWithRedirect(t *testing.T) {
 	entry := &logging.Entry{Severity: logging.Info, Payload: "test string"}
 	buffer := &strings.Builder{}
 	logger := client.Logger("test-redirect-output", logging.RedirectAsJSON(buffer))
-	onceBackup := internal.InstrumentOnce
+	onceBackup, timeBackup := internal.InstrumentOnce, logging.SetNow(testNow)
 	internal.InstrumentOnce = new(sync.Once)
 	for i := range want {
 		buffer.Reset()
@@ -1433,6 +1433,7 @@ func TestInstrumentationWithRedirect(t *testing.T) {
 			t.Errorf("got(%v), want(%v)", got, want[i])
 		}
 	}
+	logging.SetNow(timeBackup)
 	internal.InstrumentOnce = onceBackup
 }
 
diff --git a/logging/logging_unexported_test.go b/logging/logging_unexported_test.go
index 55f3f4d0e201..eb0b91c85cd4 100644
--- a/logging/logging_unexported_test.go
+++ b/logging/logging_unexported_test.go
@@ -351,6 +351,7 @@ func TestMonitoredResource(t *testing.T) {
 }
 
 // Used by the tests in logging_test.
-func SetNow(f func() time.Time) {
-	now = f
+func SetNow(f func() time.Time) func() time.Time {
+	now, f = f, now
+	return f
 }