Mongo has unexpected ObjectId for _id

I recently updated to Meteor 1.5.2 (from 1.5.1, using ‘meteor update’) and I have noticed a change in behavior. Mongo documents inserted via bulk operation have _id of type ObjectId. Before the update the types were always strings. I have confirmed this by rolling back the Meteor update and observing that the behavior reverts. Documents inserted via the regular insert API look OK (they have string _ids).

Any suggestions on how to troubleshoot? I am happy to provide additional data. Below are a few details from my commit.

Thank you,

L

package

meteor-base@1.1.0 # Packages every Meteor app needs to have
mobile-experience@1.0.4 # Packages for a great mobile UX
-mongo@1.1.19 # The database Meteor supports right now
+mongo@1.2.0 # The database Meteor supports right now
blaze-html-templates@1.0.4 # Compile .html files into Meteor Blaze views
session@1.1.7 # Client-side reactive dictionary for your app
tracker@1.1.3 # Meteor’s client-side reactive programming library

es5-shim@4.6.15 # ECMAScript 5 compatibility for older browsers.
-ecmascript@0.8.1 # Enable ECMAScript2015+ syntax in app code
+ecmascript@0.8.2 # Enable ECMAScript2015+ syntax in app code

-accounts-base@1.3.1
+accounts-base@1.3.2
accounts-google@1.2.0
accounts-oauth@1.1.15
aldeed:collection2
aldeed:simple-schema
gadicohen:sitemaps
juliancwirko:postcss
kadira:blaze-layout
kadira:flow-router
lookback:tooltips
meteorhacks:picker
meteorhacks:ssr
oauth@1.1.13
oauth2@1.1.11
-promise@0.8.9
+promise@0.9.0
standard-minifier-js@2.1.1
stuke:ics-generator
shell-server@0.2.4
force-ssl@1.0.14
react-template-helper
react-meteor-data
-google-config-ui
-google-oauth
-dynamic-import
+google-config-ui@1.0.0
+google-oauth@1.2.4
+dynamic-import@0.1.1

release

-METEOR@1.5.1
+METEOR@1.5.2

versions

-accounts-base@1.3.1
+accounts-base@1.3.2
accounts-google@1.2.0
accounts-oauth@1.1.15
aldeed:collection2@2.10.0
aldeed:collection2-core@1.2.0
aldeed:schema-deny@1.1.0
aldeed:schema-index@1.1.1
aldeed:simple-schema@1.5.3
-allow-deny@1.0.6
+allow-deny@1.0.9
autoupdate@1.3.12
-babel-compiler@6.19.4
+babel-compiler@6.20.0
babel-runtime@1.0.1
base64@1.0.10
binary-heap@1.0.10
blaze@2.3.2
blaze-html-templates@1.1.2
blaze-tools@1.0.10
-boilerplate-generator@1.1.1
+boilerplate-generator@1.2.0
caching-compiler@1.1.9
caching-html-compiler@1.1.2
callback-hook@1.0.10
check@1.2.5
coffeescript@1.11.1_4
-ddp@1.3.0
-ddp-client@2.0.0
+ddp@1.3.1
+ddp-client@2.1.2
ddp-common@1.2.9
ddp-rate-limiter@1.0.7
-ddp-server@2.0.0
+ddp-server@2.0.2
deps@1.0.12
diff-sequence@1.0.7
-dynamic-import@0.1.1
+dynamic-import@0.1.3
ecmascript@0.8.2
ecmascript-runtime@0.4.1
ecmascript-runtime-client@0.4.3
ecmascript-runtime-server@0.4.1
-ejson@1.0.13
+ejson@1.0.14
es5-shim@4.6.15
fastclick@1.0.13
-force-ssl@1.0.14
-force-ssl-common@1.0.14
+force-ssl@1.0.15
+force-ssl-common@1.0.15
gadicohen:robots-txt@0.0.10
gadicohen:sitemaps@0.0.26
geojson-utils@1.0.10
google-config-ui@1.0.0
google-oauth@1.2.4
hot-code-push@1.0.4
html-tools@1.0.11
htmljs@1.0.11
http@1.2.12
id-map@1.0.9
jquery@1.11.10
juliancwirko:postcss@1.2.0
kadira:blaze-layout@2.3.0
kadira:flow-router@2.12.1
launch-screen@1.1.1
livedata@1.0.18
localstorage@1.1.1
logging@1.1.17
lookback:tooltips@0.6.1
mdg:validation-error@0.5.1
-meteor@1.7.0
+meteor@1.7.2
meteor-base@1.1.0
meteorhacks:picker@1.0.3
meteorhacks:ssr@2.2.0
minifier-css@1.2.16
-minifier-js@2.1.1
-minimongo@1.2.1
+minifier-js@2.1.3
+minimongo@1.3.1
mobile-experience@1.0.4
mobile-status-bar@1.0.14
-modules@0.9.2
+modules@0.10.0
modules-runtime@0.8.0
-mongo@1.1.22
+mongo@1.2.2
+mongo-dev-server@1.0.1
mongo-id@1.0.6
npm-mongo@2.2.30
oauth@1.1.13
oauth2@1.1.11
observe-sequence@1.0.16
ordered-dict@1.0.9
-promise@0.8.9
+promise@0.9.0
raix:eventemitter@0.1.3
random@1.0.10
rate-limit@1.0.8
-react-meteor-data@0.2.12
+react-meteor-data@0.2.13
react-template-helper@0.2.9
reactive-dict@1.1.9
reactive-var@1.0.11
reload@1.1.11
retry@1.0.9
routepolicy@1.0.12
service-configuration@1.0.11
session@1.1.7
shell-server@0.2.4
spacebars@1.0.15
-spacebars-compiler@1.1.2
+spacebars-compiler@1.1.3
standard-minifier-js@2.1.1
stuke:ics-generator@0.1.2
templating@1.3.2
-templating-compiler@1.3.2
+templating-compiler@1.3.3
templating-runtime@1.3.2
templating-tools@1.1.2
tmeasday:check-npm-versions@0.3.1
tracker@1.1.3
ui@1.0.13
underscore@1.0.10
url@1.1.0
-webapp@1.3.17
+webapp@1.3.19
webapp-hashing@1.0.9