diff --git a/src/cmd/go/alldocs.go b/src/cmd/go/alldocs.go
index 661c7c08f6..044e776ec0 100644
--- a/src/cmd/go/alldocs.go
+++ b/src/cmd/go/alldocs.go
@@ -1404,6 +1404,7 @@ control the execution of any test:
 
 	-timeout t
 	    If a test runs longer than t, panic.
+	    The default is 10 minutes (10m).
 
 	-trace trace.out
 	    Write an execution trace to the specified file before exiting.