diff --git a/CHANGELOG.md b/CHANGELOG.md
index 81396d814..34d4e7092 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,6 @@
 # Changelog Fab Manager
 
-- Ability to configure allowing or preventing member book a machine/formation/event slot if he already have a reservation the same day at the same time
+- Ability to configure the policy (allow or prevent) for members booking a machine/formation/event slot, if they already have a reservation the same day at the same time
 - Ability to create and delete periodic calendar availabilities (recurrence)
 - Ability to fully customize the home page
 - Automated setup assistant
@@ -142,7 +142,7 @@
 ## v4.0.4 2019 August 14
 
 - Fix a bug: #140 VAT rate is erroneous in invoices.
-  Note: this bug was introduced in v4.0.3 and requires (if you are on v4.0.3)  to regenerate the invoices since August 1st (if
+  Note: this bug was introduced in v4.0.3 and requires (if you are on v4.0.3) to regenerate the invoices since August 1st
 - [TODO DEPLOY] `rake fablab:maintenance:regenerate_invoices[2019,8]`
 
 ## v4.0.3 2019 August 01
diff --git a/app/assets/javascripts/controllers/events.js.erb b/app/assets/javascripts/controllers/events.js.erb
index 4e1717060..d81811991 100644
--- a/app/assets/javascripts/controllers/events.js.erb
+++ b/app/assets/javascripts/controllers/events.js.erb
@@ -820,8 +820,7 @@ Application.Controllers.controller('ShowEventController', ['$scope', '$state', '
     };
 
     /**
-     * find user reservations the same date at the same time with event
-     *
+     * Find user's reservations, the same date at the same time, with event
      */
     var findReservationsAtSameTime = function () {
       let sameTimeReservations = [
@@ -829,18 +828,18 @@ Application.Controllers.controller('ShowEventController', ['$scope', '$state', '
         'machine_reservations',
         'space_reservations',
         'events_reservations'
-      ].map(k => {
-        return _.filter($scope.ctrl.member[k], r => {
+      ].map(function(k) {
+        return _.filter($scope.ctrl.member[k], function(r) {
           if (r.reservable_type === 'Event' && r.reservable.id === $scope.event.id) {
             return false;
-          };
+          }
           return moment($scope.event.start_time).isSame(r.start_at) ||
             (moment($scope.event.end_time).isAfter(r.start_at) && moment($scope.event.end_time).isBefore(r.end_at)) ||
             (moment($scope.event.start_time).isAfter(r.start_at) && moment($scope.event.start_time).isBefore(r.end_at)) ||
             (moment($scope.event.start_time).isBefore(r.start_at) && moment($scope.event.end_time).isAfter(r.end_at));
         });
       });
-      return _.union(...sameTimeReservations);
+      return _.union.apply(null, sameTimeReservations);
     };
 
     /**
diff --git a/app/assets/javascripts/directives/cart.js.erb b/app/assets/javascripts/directives/cart.js.erb
index 816253088..efafc2763 100644
--- a/app/assets/javascripts/directives/cart.js.erb
+++ b/app/assets/javascripts/directives/cart.js.erb
@@ -77,15 +77,15 @@ Application.Directives.directive('cart', [ '$rootScope', '$uibModal', 'dialogs',
             'machine_reservations',
             'space_reservations',
             'events_reservations'
-          ].map(k => {
-            return _.filter($scope.user[k], r => {
+          ].map(function (k) {
+            return _.filter($scope.user[k], function(r) {
               return slot.start.isSame(r.start_at) ||
                 (slot.end.isAfter(r.start_at) && slot.end.isBefore(r.end_at)) ||
                 (slot.start.isAfter(r.start_at) && slot.start.isBefore(r.end_at)) ||
                 (slot.start.isBefore(r.start_at) && slot.end.isAfter(r.end_at));
-            });
+            })
           });
-          sameTimeReservations = _.union(...sameTimeReservations);
+          sameTimeReservations = _.union.apply(null, sameTimeReservations);
           if (sameTimeReservations.length > 0) {
             const modalInstance = $uibModal.open({
               animation: true,
@@ -93,7 +93,7 @@ Application.Directives.directive('cart', [ '$rootScope', '$uibModal', 'dialogs',
               size: 'md',
               controller: 'ReserveSlotSameTimeController',
               resolve: {
-                sameTimeReservations: function() { return sameTimeReservations; },
+                sameTimeReservations: function() { return sameTimeReservations; }
               }
             });
             modalInstance.result.then(function(res) {
diff --git a/doc/environment.md b/doc/environment.md
index 7cef275b4..8e43aadb8 100644
--- a/doc/environment.md
+++ b/doc/environment.md
@@ -111,7 +111,7 @@ If set to 'false' the phone number won't be required to register a new user on t
 
     BOOK_SLOT_AT_SAME_TIME
 
-If set to 'false' user won't book a machine/formation/event slot if he already have a reservation the same day at the same time.
+If set to 'false', users won't be able to book a machine/formation/event slot if they already have a reservation the same day at the same time.
 <a name="USER_CONFIRMATION_NEEDED_TO_SIGN_IN"></a>
 
     USER_CONFIRMATION_NEEDED_TO_SIGN_IN