diff --git a/src/testing/testing.go b/src/testing/testing.go
index 402780ad649..1c3ed20585b 100644
--- a/src/testing/testing.go
+++ b/src/testing/testing.go
@@ -781,9 +781,9 @@ func tRunner(t *T, fn func(t *T)) {
 	t.finished = true
 }
 
-// Run runs f as a subtest of t called name. It reports whether f succeeded. Run
-// runs f in a separate goroutine and will block until all its parallel subtests
-// have completed.
+// Run runs f as a subtest of t called name. It runs f in a separate goroutine
+// and blocks until f returns or calls t.Parallel to become a parallel test.
+// Run reports whether f succeeded (or at least did not fail before calling t.Parallel).
 //
 // Run may be called simultaneously from multiple goroutines, but all such calls
 // must return before the outer test function for t returns.