diff --git a/lib/runtime.js b/lib/runtime.js
index e45394e..22d28d9 100644
--- a/lib/runtime.js
+++ b/lib/runtime.js
@@ -124,6 +124,7 @@ PEG.Parser.prototype = {
           case 1:
             return failuresExpected[0];
           default:
+            failuresExpected.sort();
             return failuresExpected.slice(0, failuresExpected.length - 1).join(", ")
               + " or "
               + failuresExpected[failuresExpected.length - 1];
diff --git a/test/compiler-test.js b/test/compiler-test.js
index 0d05ddc..3e7e61e 100644
--- a/test/compiler-test.js
+++ b/test/compiler-test.js
@@ -463,6 +463,13 @@ test("error messages", function() {
     "",
     'Expected "a" but end of input found.'
   );
+
+  var unsortedErrorsParser = PEG.buildParser('start: "b" / "a"');
+  doesNotParseWithMessage(
+    unsortedErrorsParser,
+    "",
+    'Expected "a" or "b" but end of input found.'
+  );
 });
 
 test("error positions", function() {