diff --git a/helpers/javascript/lib/updater.js b/helpers/javascript/lib/updater.js
index 5b7b9c91..59427a3f 100644
--- a/helpers/javascript/lib/updater.js
+++ b/helpers/javascript/lib/updater.js
@@ -61,7 +61,22 @@ async function allDependencyPatterns(config) {
   );
 }
 
+// Replace the version comments in the new lockfile with the ones from the old
+// lockfile. If they weren't present in the old lockfile, delete them.
+function recoverVersionComments(oldLockfile, newLockfile) {
+  const yarnRegex = /^# yarn v(\S+)\n/gm;
+  const nodeRegex = /^# node v(\S+)\n/gm;
+  const oldMatch = regex => [].concat(oldLockfile.match(regex))[0];
+  return newLockfile
+    .replace(yarnRegex, match => oldMatch(yarnRegex) || "")
+    .replace(nodeRegex, match => oldMatch(nodeRegex) || "");
+}
+
 async function updateDependencyFiles(directory, depName, desiredVersion) {
+  const readFile = fileName =>
+    fs.readFileSync(path.join(directory, fileName)).toString();
+  const originalYarnLock = readFile("yarn.lock");
+
   const flags = { ignoreScripts: true };
   const reporter = new NoopReporter();
   const config = new Config(reporter);
@@ -85,15 +100,11 @@ async function updateDependencyFiles(directory, depName, desiredVersion) {
   // Despite the innocent-sounding name, this actually does all the hard work
   await add.init();
 
-  const updatedYarnLock = fs
-    .readFileSync(path.join(directory, "yarn.lock"))
-    .toString();
-  const updatedPackageJson = fs
-    .readFileSync(path.join(directory, "package.json"))
-    .toString();
+  const updatedYarnLock = readFile("yarn.lock");
+  const updatedPackageJson = readFile("package.json");
 
   return {
-    "yarn.lock": updatedYarnLock,
+    "yarn.lock": recoverVersionComments(originalYarnLock, updatedYarnLock),
     "package.json": updatedPackageJson
   };
 }
diff --git a/helpers/javascript/package.json b/helpers/javascript/package.json
index 7f29bd05..15cac212 100644
--- a/helpers/javascript/package.json
+++ b/helpers/javascript/package.json
@@ -1,7 +1,7 @@
 {
   "name": "bump-core",
   "dependencies": {
-    "yarn": "^0.24.4"
+    "yarn": "https://github.com/dependabot/yarn.git"
   },
   "devDependencies": {
     "eslint": "^3.19.0",
diff --git a/helpers/javascript/test/fixtures/updater/with-version-comments/package.json b/helpers/javascript/test/fixtures/updater/with-version-comments/package.json
new file mode 100644
index 00000000..00039fe5
--- /dev/null
+++ b/helpers/javascript/test/fixtures/updater/with-version-comments/package.json
@@ -0,0 +1,5 @@
+{
+  "dependencies": {
+    "left-pad": "^1.0.0"
+  }
+}
diff --git a/helpers/javascript/test/fixtures/updater/with-version-comments/yarn.lock b/helpers/javascript/test/fixtures/updater/with-version-comments/yarn.lock
new file mode 100644
index 00000000..a051ee2c
--- /dev/null
+++ b/helpers/javascript/test/fixtures/updater/with-version-comments/yarn.lock
@@ -0,0 +1,13 @@
+# THIS IS AN AUTOGENERATED FILE. DO NOT EDIT THIS FILE DIRECTLY.
+# yarn lockfile v1
+# yarn v0.0.0-0
+# node v0.0.0
+
+
+is-positive@^3.1.0:
+  version "3.1.0"
+  resolved "https://registry.yarnpkg.com/is-positive/-/is-positive-3.1.0.tgz#857db584a1ba5d1cb2980527fc3b6c435d37b0fd"
+
+left-pad@^1.0.0:
+  version "1.0.0"
+  resolved "https://registry.yarnpkg.com/left-pad/-/left-pad-1.0.0.tgz#c84e2417581bbb8eaf2b9e3d7a122e572ab1af37"
diff --git a/helpers/javascript/test/updater.test.js b/helpers/javascript/test/updater.test.js
index c3d9b0ea..88cdf9e1 100644
--- a/helpers/javascript/test/updater.test.js
+++ b/helpers/javascript/test/updater.test.js
@@ -2,36 +2,51 @@ const path = require("path");
 const os = require("os");
 const fs = require("fs-extra");
 const nock = require("nock");
-const updater = require("../lib/updater");
+const updateDependencyFiles = require("../lib/updater").updateDependencyFiles;
 const helpers = require("./helpers");
 
 describe("updater", () => {
   let tempDir;
   beforeEach(() => {
-    tempDir = fs.mkdtempSync(os.tmpdir() + path.sep);
-  });
-  afterEach(() => fs.removeSync(tempDir));
-
-  it("something", async () => {
     nock("https://registry.yarnpkg.com")
       .get("/left-pad")
       .reply(200, helpers.loadFixture("yarnpkg-left-pad.json"));
 
-    const srcPackageJson = "test/fixtures/updater/original/package.json";
-    const destPackageJson = path.join(tempDir, "package.json");
-    await fs.copy(srcPackageJson, destPackageJson);
+    tempDir = fs.mkdtempSync(os.tmpdir() + path.sep);
+  });
+  afterEach(() => fs.removeSync(tempDir));
+
+  async function copyDependencies(sourceDir, destDir) {
+    const srcPackageJson = `test/fixtures/updater/${sourceDir}/package.json`;
+    await fs.copy(srcPackageJson, `${destDir}/package.json`);
 
-    const srcYarnLock = "test/fixtures/updater/original/yarn.lock";
-    const destYarnLock = path.join(tempDir, "yarn.lock");
-    await fs.copy(srcYarnLock, destYarnLock);
+    const srcYarnLock = `test/fixtures/updater/${sourceDir}/yarn.lock`;
+    await fs.copy(srcYarnLock, `${destDir}/yarn.lock`);
+  }
 
-    const name = "left-pad";
-    const version = "1.1.3";
-    const result = await updater.updateDependencyFiles(tempDir, name, version);
+  it("generates an updated package.json and yarn.lock", async () => {
+    await copyDependencies("original", tempDir);
 
+    const result = await updateDependencyFiles(tempDir, "left-pad", "1.1.3");
     expect(result).toEqual({
       "package.json": helpers.loadFixture("updater/updated/package.json"),
       "yarn.lock": helpers.loadFixture("updater/updated/yarn.lock")
     });
   });
+
+  it("doesn't modify existing version comments", async () => {
+    await copyDependencies("with-version-comments", tempDir);
+
+    const result = await updateDependencyFiles(tempDir, "left-pad", "1.1.3");
+    expect(result["yarn.lock"]).toContain("\n# yarn v0.0.0-0\n");
+    expect(result["yarn.lock"]).toContain("\n# node v0.0.0\n");
+  });
+
+  it("doesn't add version comments if they're not already there", async () => {
+    await copyDependencies("original", tempDir);
+
+    const result = await updateDependencyFiles(tempDir, "left-pad", "1.1.3");
+    expect(result["yarn.lock"]).not.toContain("\n# yarn v");
+    expect(result["yarn.lock"]).not.toContain("\n# node");
+  });
 });
diff --git a/helpers/javascript/yarn.lock b/helpers/javascript/yarn.lock
index c998e3f0..1bd4a48c 100644
--- a/helpers/javascript/yarn.lock
+++ b/helpers/javascript/yarn.lock
@@ -1,5 +1,7 @@
 # THIS IS AN AUTOGENERATED FILE. DO NOT EDIT THIS FILE DIRECTLY.
 # yarn lockfile v1
+# yarn v0.24.4
+# node v7.10.0
 
 
 abab@^1.0.3:
@@ -2912,9 +2914,9 @@ yargs@~3.10.0:
     decamelize "^1.0.0"
     window-size "0.1.0"
 
-yarn@^0.24.4:
-  version "0.24.4"
-  resolved "https://registry.yarnpkg.com/yarn/-/yarn-0.24.4.tgz#a4bfa3bb768192706771337f959721cfc0555093"
+"yarn@https://github.com/dependabot/yarn.git":
+  version "0.26.0-0"
+  resolved "https://github.com/dependabot/yarn.git#c1c19d6b735b35cbc07425f6469f48c2284bb807"
   dependencies:
     babel-runtime "^6.0.0"
     bytes "^2.4.0"
@@ -2925,6 +2927,7 @@ yarn@^0.24.4:
     death "^1.0.0"
     debug "^2.2.0"
     detect-indent "^5.0.0"
+    glob "^7.1.1"
     gunzip-maybe "^1.4.0"
     ini "^1.3.4"
     inquirer "^3.0.1"
@@ -2933,7 +2936,7 @@ yarn@^0.24.4:
     is-ci "^1.0.10"
     leven "^2.0.0"
     loud-rejection "^1.2.0"
-    minimatch "^3.0.3"
+    micromatch "^2.3.11"
     mkdirp "^0.5.1"
     node-emoji "^1.0.4"
     object-path "^0.11.2"