diff --git a/src/libstd/net_url.rs b/src/libstd/net_url.rs
index 90c5e037e4d6..d046dec52259 100644
--- a/src/libstd/net_url.rs
+++ b/src/libstd/net_url.rs
@@ -644,6 +644,11 @@ fn to_str(url: url) -> ~str {
     } else {
        ~""
     };
+    let authority = if str::len(url.host) != 0 {
+        str::concat(~[~"//", user, copy url.host])
+    } else {
+        ~""
+    };
     let query = if url.query.len() == 0 {
         ~""
     } else {
@@ -657,12 +662,11 @@ fn to_str(url: url) -> ~str {
     };
 
     return str::concat(~[copy url.scheme,
-                      ~"://",
-                      user,
-                      copy url.host,
-                      copy url.path,
-                      query,
-                      fragment]);
+                         ~":",
+                         authority,
+                         copy url.path,
+                         query,
+                         fragment]);
 }
 
 impl of to_str::to_str for url {
@@ -849,6 +853,12 @@ mod tests {
             .get().second() == ~"#&+";
     }
 
+    #[test]
+    fn test_url_without_authority() {
+        let url = ~"mailto:test@email.com";
+        assert to_str(result::unwrap(from_str(url))) == url;
+    }
+
     #[test]
     fn test_encode() {
         assert encode(~"") == ~"";