diff --git a/README.md b/README.md
index 24dbcbf78..237541741 100644
--- a/README.md
+++ b/README.md
@@ -1,5 +1,5 @@
 <h1><p align="center"><img alt="protobuf.js" src="https://github.com/dcodeIO/protobuf.js/raw/master/pbjs.png" width="120" height="104" /></p></h1>
-<p align="center"><a href="https://travis-ci.org/dcodeIO/protobuf.js"><img src="https://travis-ci.org/dcodeIO/protobuf.js.svg?branch=master" alt=""></a> <a href="https://codeclimate.com/github/dcodeIO/protobuf.js/coverage"><img src="https://codeclimate.com/github/dcodeIO/protobuf.js/badges/coverage.svg" /></a> <a href="https://codeclimate.com/github/dcodeIO/protobuf.js"><img src="https://codeclimate.com/github/dcodeIO/protobuf.js/badges/gpa.svg" /></a> <a href="https://npmjs.org/package/protobufjs"><img src="https://img.shields.io/npm/dm/protobufjs.svg" alt=""></a> <a href="https://npmjs.org/package/protobufjs"><img src="https://img.shields.io/npm/v/protobufjs.svg" alt=""></a> <a href="https://www.paypal.com/cgi-bin/webscr?cmd=_donations&business=dcode%40dcode.io&item_name=Open%20Source%20Software%20Donation&item_number=dcodeIO%2Fprotobuf.js"><img alt="donate ❤" src="https://img.shields.io/badge/donate-❤-ff2244.svg"></a></p>
+<p align="center"><a href="https://npmjs.org/package/protobufjs"><img src="https://img.shields.io/npm/v/protobufjs.svg" alt=""></a> <a href="https://travis-ci.org/dcodeIO/protobuf.js"><img src="https://travis-ci.org/dcodeIO/protobuf.js.svg?branch=master" alt=""></a> <a href="https://codeclimate.com/github/dcodeIO/protobuf.js/coverage"><img src="https://codeclimate.com/github/dcodeIO/protobuf.js/badges/coverage.svg" /></a> <a href="https://codeclimate.com/github/dcodeIO/protobuf.js"><img src="https://codeclimate.com/github/dcodeIO/protobuf.js/badges/gpa.svg" /></a> <a href="https://npmjs.org/package/protobufjs"><img src="https://img.shields.io/npm/dm/protobufjs.svg" alt=""></a> <a href="https://www.paypal.com/cgi-bin/webscr?cmd=_donations&business=dcode%40dcode.io&item_name=Open%20Source%20Software%20Donation&item_number=dcodeIO%2Fprotobuf.js"><img alt="donate ❤" src="https://img.shields.io/badge/donate-❤-ff2244.svg"></a></p>
 
 **Protocol Buffers** are a language-neutral, platform-neutral, extensible way of serializing structured data for use in communications protocols, data storage, and more, originally designed at Google ([see](https://developers.google.com/protocol-buffers/)).
 
@@ -346,7 +346,7 @@ Documentation
 * [Frequently asked questions](https://github.com/dcodeIO/protobuf.js/wiki) on our wiki
 
 #### Community
-* [Questions and answers](http://stackoverflow.com/search?q=protobuf.js) on StackOverflow
+* [Questions and answers](http://stackoverflow.com/search?tab=newest&q=protobuf.js) on StackOverflow
 
 Command line
 ------------
diff --git a/src/encoder.js b/src/encoder.js
index e7b304f94..b2586c733 100644
--- a/src/encoder.js
+++ b/src/encoder.js
@@ -49,12 +49,13 @@ function encoder(mtype) {
 
     // "when a message is serialized its known fields should be written sequentially by field number"
     var fields = /* initializes */ mtype.fieldsArray;
+    /* istanbul ignore else */
     if (encoder.compat)
         fields = fields.slice().sort(compareFieldsById);
 
     for (var i = 0; i < fields.length; ++i) {
         var field    = fields[i].resolve(),
-            index    = encoder.compat ? mtype._fieldsArray.indexOf(field) : i;
+            index    = encoder.compat ? mtype._fieldsArray.indexOf(field) : /* istanbul ignore next */ i;
         if (field.partOf) // see below for oneofs
             continue;
         var type     = field.resolvedType instanceof Enum ? "uint32" : field.type,
diff --git a/tests/other_protocolerror.js b/tests/other_protocolerror.js
index 076cae5c1..3030a6d47 100644
--- a/tests/other_protocolerror.js
+++ b/tests/other_protocolerror.js
@@ -27,6 +27,8 @@ tape.test("a protocol error", function(test) {
         test.fail("should be thrown if a message is missing required fields");
     } catch (e) {
         test.ok(e instanceof ProtocolError, "should be thrown if a message is missing required fields");
+        test.ok(e.message, "should have an error message");
+        test.ok(e.stack, "should have a stack trace");
         test.equal(e.name, "ProtocolError", "should have the correct name");
         test.same(e.instance, {
             foo: 2