diff --git a/services/sync/modules/identity.js b/services/sync/modules/identity.js
index 7963b02ee3c..82e690046e9 100644
--- a/services/sync/modules/identity.js
+++ b/services/sync/modules/identity.js
@@ -85,7 +85,7 @@ Identity.prototype = {
     // Look up the password then cache it
     if (this._password == null)
       for each (let login in this._logins)
-        if (login.username == this.username)
+        if (login.username.toLowerCase() == this.username)
           this._password = login.password;
     return this._password;
   },
diff --git a/services/sync/modules/service.js b/services/sync/modules/service.js
index d6a2046f576..1c8ec68c61a 100644
--- a/services/sync/modules/service.js
+++ b/services/sync/modules/service.js
@@ -108,11 +108,14 @@ WeaveSvc.prototype = {
   _keyPair: {},
 
   get username() {
-    return Svc.Prefs.get("username", "");
+    return Svc.Prefs.get("username", "").toLowerCase();
   },
   set username(value) {
-    if (value)
+    if (value) {
+      // Make sure all uses of this new username is lowercase
+      value = value.toLowerCase();
       Svc.Prefs.set("username", value);
+    }
     else
       Svc.Prefs.reset("username");