diff --git a/userdata.go b/userdata.go
index 59a082b..aea4d39 100644
--- a/userdata.go
+++ b/userdata.go
@@ -52,7 +52,7 @@ func (u *UserData) String() (s string, err error) {
 	if err != nil {
 		return
 	}
-	s = base64.StdEncoding.EncodeToString(b)
+	s = url.QueryEscape(base64.StdEncoding.EncodeToString(b))
 	return
 }