diff --git a/packages/livedata/livedata_common.js b/packages/livedata/livedata_common.js
index 7f88ada63d..7064c6272b 100644
--- a/packages/livedata/livedata_common.js
+++ b/packages/livedata/livedata_common.js
@@ -109,6 +109,11 @@ Meteor._stringifyDDP = function (msg) {
 
 Meteor._CurrentInvocation = new Meteor.EnvironmentVariable;
 
+// Note: The DDP server assumes that Meteor.Error EJSON-serializes as an object
+// containing 'error' and optionally 'reason' and 'details'.
+// The DDP client manually puts these into Meteor.Error objects. (We don't use
+// EJSON.addType here because the type is determined by location in the
+// protocol, not text on the wire.)
 Meteor.Error = function (error, reason, details) {
   var self = this;
 
diff --git a/packages/livedata/livedata_connection.js b/packages/livedata/livedata_connection.js
index f2b01f7a7f..466427c837 100644
--- a/packages/livedata/livedata_connection.js
+++ b/packages/livedata/livedata_connection.js
@@ -1191,7 +1191,6 @@ _.extend(Meteor._LivedataConnection.prototype, {
     currentMethodBlock.splice(i, 1);
 
     if (_.has(msg, 'error')) {
-      // XXX should we hook Meteor.Error in to EJSON?
       m.receiveResult(new Meteor.Error(
         msg.error.error, msg.error.reason,
         msg.error.details));
diff --git a/packages/livedata/livedata_connection_tests.js b/packages/livedata/livedata_connection_tests.js
index 3ba2c350ed..f32c724b53 100644
--- a/packages/livedata/livedata_connection_tests.js
+++ b/packages/livedata/livedata_connection_tests.js
@@ -1418,7 +1418,7 @@ Tinytest.add("livedata stub - subscribe failure", function (test) {
 
   // Reject the sub.
   stream.receive({msg: 'nosub', id: subMessage.id,
-                  error: {error: 404, reason: "Subscription not found"}});
+                  error: new Meteor.Error(404, "Subscription not found")});
   test.isFalse(onReadyFired);
   test.instanceOf(subError, Meteor.Error);
   test.equal(subError.error, 404);
diff --git a/packages/livedata/livedata_server.js b/packages/livedata/livedata_server.js
index a35d386eba..8868908c25 100644
--- a/packages/livedata/livedata_server.js
+++ b/packages/livedata/livedata_server.js
@@ -569,7 +569,7 @@ _.extend(Meteor._LivedataSession.prototype, {
       if (!handler) {
         self.send({
           msg: 'result', id: msg.id,
-          error: {error: 404, reason: "Method not found"}});
+          error: new Meteor.Error(404, "Method not found")});
         fence.arm();
         return;
       }
diff --git a/packages/test-helpers/package.js b/packages/test-helpers/package.js
index 663d9d63d9..ff065d5b5d 100644
--- a/packages/test-helpers/package.js
+++ b/packages/test-helpers/package.js
@@ -6,6 +6,8 @@ Package.describe({
 Package.on_use(function (api, where) {
   where = where || ["client", "server"];
 
+  api.use('ejson');
+
   // XXX These files have various dependencies on other packages
   // that aren't specified here. :(
   // This package should probably get split into several packages,
diff --git a/packages/test-helpers/stub_stream.js b/packages/test-helpers/stub_stream.js
index 1ca1491302..ff32dbc650 100644
--- a/packages/test-helpers/stub_stream.js
+++ b/packages/test-helpers/stub_stream.js
@@ -36,7 +36,7 @@ _.extend(Meteor._StubStream.prototype, {
     var self = this;
 
     if (typeof data === 'object') {
-      data = JSON.stringify(data);
+      data = EJSON.stringify(data);
     }
 
     _.each(self.callbacks['message'], function (cb) {