diff --git a/app/assets/javascripts/results/result_assets.js b/app/assets/javascripts/results/result_assets.js
index 73aade08e..8639efd60 100644
--- a/app/assets/javascripts/results/result_assets.js
+++ b/app/assets/javascripts/results/result_assets.js
@@ -67,7 +67,14 @@ function formAjaxResultAsset($form) {
     reloadImages($imgs);
   })
   .on("ajax:error", function(e, data) {
-    $form.renderFormErrors("result", data.errors, true, e);
+    // This check is here only because of remotipart bug, which returns
+    // HTML instead of JSON, go figure
+    var errors = '';
+    if (data.errors)
+      errors = data.errors;
+    else
+      errors = data.responseJSON.errors;
+    $form.renderFormErrors("result", errors, true, e);
   });
 }
 
diff --git a/app/controllers/result_assets_controller.rb b/app/controllers/result_assets_controller.rb
index 80adafce1..f9d25b8af 100644
--- a/app/controllers/result_assets_controller.rb
+++ b/app/controllers/result_assets_controller.rb
@@ -103,6 +103,7 @@ class ResultAssetsController < ApplicationController
   def update
     update_params = result_params
     previous_size = @result.space_taken
+    previous_asset = @result.asset
 
     if update_params.key? :asset_attributes
       asset = Asset.find_by_id(update_params[:asset_attributes][:id])
@@ -136,6 +137,19 @@ class ResultAssetsController < ApplicationController
     elsif @result.archived_changed?(from: true, to: false)
       render_403
     else
+      if previous_asset.locked?
+        @result.errors.add(:asset_attributes,
+                           I18n.t('result_assets.edit.locked_file_error'))
+        respond_to do |format|
+          format.json do
+            render json: {
+              status: 'error',
+              errors: @result.errors
+            }, status: :bad_request
+            return
+          end
+        end
+      end
       # Asset (file) and/or name has been changed
       saved = @result.save
 
diff --git a/config/locales/en.yml b/config/locales/en.yml
index da60b9203..2e8c8725f 100644
--- a/config/locales/en.yml
+++ b/config/locales/en.yml
@@ -837,6 +837,7 @@ en:
       title: "Edit result from task %{module}"
       uploaded_asset: "Uploaded file"
       update: "Update file result"
+      locked_file_error: 'This file is being edited by someone else.'
     create:
       success_flash: "Successfully added file result to task <strong>%{module}</strong>"
     update: