diff --git a/src/pkg/os/file.go b/src/pkg/os/file.go
index 83b022aa0ae..75c0561e9ec 100644
--- a/src/pkg/os/file.go
+++ b/src/pkg/os/file.go
@@ -97,6 +97,9 @@ func (file *File) Close() Error {
 		err = &PathError{"close", file.name, Errno(e)}
 	}
 	file.fd = -1 // so it can't be closed again
+
+	// no need for a finalizer anymore
+	runtime.SetFinalizer(file, nil)
 	return err
 }