diff --git a/src/testing/testing.go b/src/testing/testing.go
index 7e936f0fca..edee89c999 100644
--- a/src/testing/testing.go
+++ b/src/testing/testing.go
@@ -178,6 +178,9 @@
 //         }
 //     }
 //
+// The race detector kills the program if it exceeds 8192 concurrent goroutines,
+// so use care when running parallel tests with the -race flag set.
+//
 // Run does not return until parallel subtests have completed, providing a way
 // to clean up after a group of parallel tests:
 //