diff --git a/src/testing/testing.go b/src/testing/testing.go
index 6237da9abd..c478adea9f 100644
--- a/src/testing/testing.go
+++ b/src/testing/testing.go
@@ -418,10 +418,12 @@ func (c *common) Skipped() bool {
 // Parallel signals that this test is to be run in parallel with (and only with)
 // other parallel tests.
 func (t *T) Parallel() {
+	// We don't want to include the time we spend waiting for serial tests
+	// in the test duration. Record the elapsed time thus far and reset the
+	// timer afterwards.
+	t.duration += time.Since(t.start)
 	t.signal <- (*T)(nil) // Release main testing loop
 	<-t.startParallel     // Wait for serial tests to finish
-	// Assuming Parallel is the first thing a test does, which is reasonable,
-	// reinitialize the test's start time because it's actually starting now.
 	t.start = time.Now()
 }
 
@@ -438,7 +440,7 @@ func tRunner(t *T, test *InternalTest) {
 	// a call to runtime.Goexit, record the duration and send
 	// a signal saying that the test is done.
 	defer func() {
-		t.duration = time.Now().Sub(t.start)
+		t.duration += time.Now().Sub(t.start)
 		// If the test panicked, print any test output before dying.
 		err := recover()
 		if !t.finished && err == nil {