diff --git a/CHANGELOG.md b/CHANGELOG.md
index bb3db7540..86325760f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,7 @@
 ## next release
 - Improved automated testing
 - Added an information notice about the processing time of deleting an administrator
+- Ability to change the expiration date of a coupon after its creation
 - Fix a bug: unable to run rake db:migrate on first install
 - Fix a bug: unable to create or edit a coupon of type 'percentage'
 
diff --git a/app/assets/javascripts/controllers/admin/coupons.coffee b/app/assets/javascripts/controllers/admin/coupons.coffee
index 5433d4248..c62693e80 100644
--- a/app/assets/javascripts/controllers/admin/coupons.coffee
+++ b/app/assets/javascripts/controllers/admin/coupons.coffee
@@ -73,6 +73,9 @@ Application.Controllers.controller "EditCouponController", ["$scope", "$state",
   ## Options for the validity per user
   $scope.validities = userValidities
 
+  ## Mapping for validation errors
+  $scope.errors = {}
+
   ## Default parameters for AngularUI-Bootstrap datepicker (used for coupon validity limit selection)
   $scope.datePicker =
     format: Fablab.uibDateFormat
@@ -98,11 +101,12 @@ Application.Controllers.controller "EditCouponController", ["$scope", "$state",
   # Callback to save the coupon's changes to the API
   ##
   $scope.updateCoupon = ->
+    $scope.errors = {}
     Coupon.update {id: $scope.coupon.id}, coupon: $scope.coupon, (coupon) ->
       $state.go('app.admin.pricing')
     , (err)->
       growl.error(_t('unable_to_update_the_coupon_an_error_occurred'))
-      console.error(err)
+      $scope.errors = err.data
 
 
 
diff --git a/app/assets/templates/admin/coupons/_form.html.erb b/app/assets/templates/admin/coupons/_form.html.erb
index 87ce08937..9a54b7995 100644
--- a/app/assets/templates/admin/coupons/_form.html.erb
+++ b/app/assets/templates/admin/coupons/_form.html.erb
@@ -81,7 +81,7 @@
   <span class="help-block error" ng-show="couponForm['coupon[validity_per_user]'].$dirty && couponForm['coupon[validity_per_user]'].$error.required" translate>{{ 'validity_per_user_is_required' }}</span>
 </div>
 
-<div class="form-group">
+<div class="form-group" ng-class="{'has-error': errors['valid_until']}">
   <label for="coupon[valid_until]" translate>{{ 'valid_until' }}</label>
   <div class="input-group">
     <input type="text" id="coupon[valid_until]"
@@ -97,10 +97,11 @@
       <button type="button" class="btn btn-default" ng-click="toggleDatePicker($event)" ng-disabled="mode == 'EDIT'"><i class="fa fa-calendar"></i></button>
     </span>
   </div>
+  <span class="help-block error" ng-show="errors['valid_until']">{{ errors['valid_until'].join(' ; ') }}</span>
 
-  <span class="help-block text-info text-xs">
-      <i class="fa fa-lightbulb-o"></i> {{ 'leave_empty_for_no_limit' | translate }}
-    </span>
+  <span class="text-info text-xs">
+    <i class="fa fa-lightbulb-o"></i> {{ 'leave_empty_for_no_limit' | translate }}
+  </span>
 </div>
 
 <div class="form-group" ng-class="{'has-error': couponForm['coupon[max_usages]'].$dirty && couponForm['coupon[max_usages]'].$invalid}">
@@ -113,7 +114,7 @@
          min="0"/>
   <span class="help-block error" ng-show="couponForm['coupon[max_usages]'].$dirty && couponForm['coupon[max_usages]'].$error.min" translate>{{ 'max_usages_must_be_equal_or_greater_than_0' }}</span>
 
-  <span class="help-block text-info text-xs">
+  <span class="text-info text-xs">
     <i class="fa fa-lightbulb-o"></i> {{ 'leave_empty_for_no_limit' | translate }}
   </span>
 </div>
diff --git a/app/validators/coupon_discount_validator.rb b/app/validators/coupon_discount_validator.rb
index 072ae089f..60a674804 100644
--- a/app/validators/coupon_discount_validator.rb
+++ b/app/validators/coupon_discount_validator.rb
@@ -2,14 +2,14 @@ class CouponDiscountValidator < ActiveModel::Validator
   def validate(record)
     if !record.percent_off.nil?
       unless (0..100).include? record.percent_off
-        record.errors[:percent_off] << 'Percentage must be included between 0 and 100'
+        record.errors[:percent_off] << I18n.t('errors.messages.percentage_out_of_range')
       end
     elsif !record.amount_off.nil?
       unless record.amount_off > 0
         record.errors[:amount_off] << I18n.t('errors.messages.greater_than_or_equal_to', count: 0)
       end
     else
-      record.errors[:percent_off] << 'cannot be blank when amount_off is blank too'
+      record.errors[:percent_off] << I18n.t('errors.messages.cannot_be_blank_at_same_time', field: 'amount_off')
     end
   end
 end
\ No newline at end of file
diff --git a/app/validators/coupon_expiration_validator.rb b/app/validators/coupon_expiration_validator.rb
index b6ecf3892..d9a80f55e 100644
--- a/app/validators/coupon_expiration_validator.rb
+++ b/app/validators/coupon_expiration_validator.rb
@@ -8,11 +8,11 @@ class CouponExpirationValidator < ActiveModel::Validator
 
     unless current.blank?
       if current.end_of_day < Time.now
-        record.errors[:valid_until] << 'New expiration date cannot be in the past'
+        record.errors[:valid_until] << I18n.t('errors.messages.cannot_be_in_the_past')
       end
 
       if !previous.blank? and current.end_of_day < previous.end_of_day
-        record.errors[:valid_until] << 'New expiration date cannot be before the previous one'
+        record.errors[:valid_until] << I18n.t('errors.messages.cannot_be_before_previous_value')
       end
     end
   end
diff --git a/config/locales/en.yml b/config/locales/en.yml
index f30febc5e..11dbd5fd8 100644
--- a/config/locales/en.yml
+++ b/config/locales/en.yml
@@ -32,6 +32,10 @@ en:
       size_too_small: "is too small (should be at least %{file_size})"
       size_too_big: "is too big (should be at most %{file_size})"
       export_not_found: "Requested export was not found. It was probably deleted, please generate a new export."
+      percentage_out_of_range: "Percentage must be included between 0 and 100"
+      cannot_be_blank_at_same_time: "cannot be blank when %{field} is blank too"
+      cannot_be_in_the_past: "cannot be in the past"
+      cannot_be_before_previous_value: "cannot be before the previous value"
 
   activemodel:
     errors:
diff --git a/config/locales/fr.yml b/config/locales/fr.yml
index 68bb7179c..1cebdb59d 100644
--- a/config/locales/fr.yml
+++ b/config/locales/fr.yml
@@ -32,6 +32,10 @@ fr:
       size_too_small: "est trop petite (au moins %{file_size})"
       size_too_big: "est trop grande (pas plus de %{file_size})"
       export_not_found: "L'export demandé n'a pas été trouvé. Il a probablement été supprimé, veuillez lancer la génération d'un nouvel export."
+      percentage_out_of_range: "Le pourcentage doit être inclus entre 0 et 100"
+      cannot_be_blank_at_same_time: "ou %{field} doit être rempli(e)"
+      cannot_be_in_the_past: "ne peut pas être dans le passé"
+      cannot_be_before_previous_value: "ne peut pas être antérieur(e) à la valeur précédente"
 
   activemodel:
     errors: