diff --git a/services/sync/modules/engines.js b/services/sync/modules/engines.js
index 5a7837e6a971..d2dc512b543c 100644
--- a/services/sync/modules/engines.js
+++ b/services/sync/modules/engines.js
@@ -207,7 +207,7 @@ function LegacyTracker(name, engine) {
   this._ignored = [];
   this.file = this.name;
   this._storage = new JSONFile({
-    path: Utils.jsonFilePath("changes/" + this.file),
+    path: Utils.jsonFilePath("changes", this.file),
     dataPostProcessor: json => this._dataPostProcessor(json),
     beforeSave: () => this._beforeSave(),
   });
@@ -767,13 +767,13 @@ function SyncEngine(name, service) {
   this._log.debug("Engine constructed");
 
   this._toFetchStorage = new JSONFile({
-    path: Utils.jsonFilePath("toFetch/" + this.name),
+    path: Utils.jsonFilePath("toFetch", this.name),
     dataPostProcessor: json => this._metadataPostProcessor(json),
     beforeSave: () => this._beforeSaveMetadata(),
   });
 
   this._previousFailedStorage = new JSONFile({
-    path: Utils.jsonFilePath("failed/" + this.name),
+    path: Utils.jsonFilePath("failed", this.name),
     dataPostProcessor: json => this._metadataPostProcessor(json),
     beforeSave: () => this._beforeSaveMetadata(),
   });
diff --git a/services/sync/modules/util.js b/services/sync/modules/util.js
index 0f893dd7a1ea..f0a455d45f6c 100644
--- a/services/sync/modules/util.js
+++ b/services/sync/modules/util.js
@@ -348,9 +348,14 @@ var Utils = {
     ).slice(0, SYNC_KEY_DECODED_LENGTH);
   },
 
-  jsonFilePath(filePath) {
-    return OS.Path.normalize(
-      OS.Path.join(OS.Constants.Path.profileDir, "weave", filePath + ".json")
+  jsonFilePath(...args) {
+    let [fileName] = args.splice(-1);
+
+    return PathUtils.join(
+      Services.dirsvc.get("ProfD", Ci.nsIFile).path,
+      "weave",
+      ...args,
+      `${fileName}.json`
     );
   },
 
@@ -359,7 +364,6 @@ var Utils = {
    *
    * @param filePath
    *        JSON file path load from profile. Loaded file will be
-   *        <profile>/<filePath>.json. i.e. Do not specify the ".json"
    *        extension.
    * @param that
    *        Object to use for logging.
@@ -368,10 +372,15 @@ var Utils = {
    *        Promise resolved when the write has been performed.
    */
   async jsonLoad(filePath, that) {
-    let path = Utils.jsonFilePath(filePath);
+    let path;
+    if (Array.isArray(filePath)) {
+      path = Utils.jsonFilePath(...filePath);
+    } else {
+      path = Utils.jsonFilePath(filePath);
+    }
 
     if (that._log && that._log.trace) {
-      that._log.trace("Loading json from disk: " + filePath);
+      that._log.trace("Loading json from disk: " + path);
     }
 
     try {
diff --git a/services/sync/tests/unit/test_tracker_addChanged.js b/services/sync/tests/unit/test_tracker_addChanged.js
index b7aa12b4370b..385ac461bd74 100644
--- a/services/sync/tests/unit/test_tracker_addChanged.js
+++ b/services/sync/tests/unit/test_tracker_addChanged.js
@@ -52,6 +52,6 @@ add_task(async function test_tracker_persistence() {
   const changes = await tracker.getChangedIDs();
   Assert.equal(5, changes[id]);
 
-  let json = await Utils.jsonLoad("changes/tracker", tracker);
+  let json = await Utils.jsonLoad(["changes", "tracker"], tracker);
   Assert.equal(5, json[id]);
 });