diff --git a/app/controllers/admin/custom_emojis_controller.rb b/app/controllers/admin/custom_emojis_controller.rb
index cbd7abe958b..daa1460fbff 100644
--- a/app/controllers/admin/custom_emojis_controller.rb
+++ b/app/controllers/admin/custom_emojis_controller.rb
@@ -5,7 +5,7 @@ module Admin
     before_action :set_custom_emoji, except: [:index, :new, :create]
 
     def index
-      @custom_emojis = filtered_custom_emojis.page(params[:page])
+      @custom_emojis = filtered_custom_emojis.eager_load(:local_counterpart).page(params[:page])
     end
 
     def new
@@ -36,9 +36,9 @@ module Admin
     end
 
     def copy
-      emoji = CustomEmoji.new(domain: nil, shortcode: @custom_emoji.shortcode, image: @custom_emoji.image)
+      emoji = CustomEmoji.find_or_create_by(domain: nil, shortcode: @custom_emoji.shortcode)
 
-      if emoji.save
+      if emoji.update(image: @custom_emoji.image)
         flash[:notice] = I18n.t('admin.custom_emojis.copied_msg')
       else
         flash[:alert] = I18n.t('admin.custom_emojis.copy_failed_msg')
diff --git a/app/helpers/application_helper.rb b/app/helpers/application_helper.rb
index 6d625e7db9c..310e1b1b142 100644
--- a/app/helpers/application_helper.rb
+++ b/app/helpers/application_helper.rb
@@ -43,6 +43,10 @@ module ApplicationHelper
     content_tag(:i, nil, attributes.merge(class: class_names.join(' ')))
   end
 
+  def custom_emoji_tag(custom_emoji)
+    image_tag(custom_emoji.image.url, class: 'emojione', alt: ":#{custom_emoji.shortcode}:")
+  end
+
   def opengraph(property, content)
     tag(:meta, content: content, property: property)
   end
diff --git a/app/models/custom_emoji.rb b/app/models/custom_emoji.rb
index 28b6a2b0bce..a77b53c98b3 100644
--- a/app/models/custom_emoji.rb
+++ b/app/models/custom_emoji.rb
@@ -25,6 +25,8 @@ class CustomEmoji < ApplicationRecord
     :(#{SHORTCODE_RE_FRAGMENT}):
     (?=[^[:alnum:]:]|$)/x
 
+  has_one :local_counterpart, -> { where(domain: nil) }, class_name: 'CustomEmoji', primary_key: :shortcode, foreign_key: :shortcode
+
   has_attached_file :image, styles: { static: { format: 'png', convert_options: '-coalesce -strip' } }
 
   validates_attachment :image, content_type: { content_type: 'image/png' }, presence: true, size: { in: 0..50.kilobytes }
diff --git a/app/views/admin/custom_emojis/_custom_emoji.html.haml b/app/views/admin/custom_emojis/_custom_emoji.html.haml
index 399d13bbd60..bab34bc8d7e 100644
--- a/app/views/admin/custom_emojis/_custom_emoji.html.haml
+++ b/app/views/admin/custom_emojis/_custom_emoji.html.haml
@@ -1,6 +1,6 @@
 %tr
   %td
-    = image_tag custom_emoji.image.url, class: 'emojione', alt: ":#{custom_emoji.shortcode}:"
+    = custom_emoji_tag(custom_emoji)
   %td
     %samp= ":#{custom_emoji.shortcode}:"
   %td
@@ -15,7 +15,10 @@
       - else
         = table_link_to 'eye-slash', t('admin.custom_emojis.unlisted'), admin_custom_emoji_path(custom_emoji, custom_emoji: { visible_in_picker: true }), method: :patch
     - else
-      = table_link_to 'copy', t('admin.custom_emojis.copy'), copy_admin_custom_emoji_path(custom_emoji, page: params[:page]), method: :post
+      - if custom_emoji.local_counterpart.present?
+        = link_to safe_join([custom_emoji_tag(custom_emoji.local_counterpart), t('admin.custom_emojis.overwrite')]), copy_admin_custom_emoji_path(custom_emoji, page: params[:page]), method: :post, class: 'table-action-link'
+      - else
+        = table_link_to 'copy', t('admin.custom_emojis.copy'), copy_admin_custom_emoji_path(custom_emoji, page: params[:page]), method: :post
   %td
     - if custom_emoji.disabled?
       = table_link_to 'power-off', t('admin.custom_emojis.enable'), enable_admin_custom_emoji_path(custom_emoji), method: :post, data: { confirm: t('admin.accounts.are_you_sure') }
diff --git a/config/brakeman.ignore b/config/brakeman.ignore
index f198eebac2b..f7cf89dffa1 100644
--- a/config/brakeman.ignore
+++ b/config/brakeman.ignore
@@ -10,7 +10,7 @@
       "line": 122,
       "link": "http://brakemanscanner.org/docs/warning_types/link_to_href",
       "code": "link_to(Account.find(params[:id]).inbox_url, Account.find(params[:id]).inbox_url)",
-      "render_path": [{"type":"controller","class":"Admin::AccountsController","method":"show","line":13,"file":"app/controllers/admin/accounts_controller.rb"}],
+      "render_path": [{"type":"controller","class":"Admin::AccountsController","method":"show","line":15,"file":"app/controllers/admin/accounts_controller.rb"}],
       "location": {
         "type": "template",
         "template": "admin/accounts/show"
@@ -29,7 +29,7 @@
       "line": 128,
       "link": "http://brakemanscanner.org/docs/warning_types/link_to_href",
       "code": "link_to(Account.find(params[:id]).shared_inbox_url, Account.find(params[:id]).shared_inbox_url)",
-      "render_path": [{"type":"controller","class":"Admin::AccountsController","method":"show","line":13,"file":"app/controllers/admin/accounts_controller.rb"}],
+      "render_path": [{"type":"controller","class":"Admin::AccountsController","method":"show","line":15,"file":"app/controllers/admin/accounts_controller.rb"}],
       "location": {
         "type": "template",
         "template": "admin/accounts/show"
@@ -48,7 +48,7 @@
       "line": 35,
       "link": "http://brakemanscanner.org/docs/warning_types/link_to_href",
       "code": "link_to(Account.find(params[:id]).url, Account.find(params[:id]).url)",
-      "render_path": [{"type":"controller","class":"Admin::AccountsController","method":"show","line":13,"file":"app/controllers/admin/accounts_controller.rb"}],
+      "render_path": [{"type":"controller","class":"Admin::AccountsController","method":"show","line":15,"file":"app/controllers/admin/accounts_controller.rb"}],
       "location": {
         "type": "template",
         "template": "admin/accounts/show"
@@ -57,25 +57,6 @@
       "confidence": "Weak",
       "note": ""
     },
-    {
-      "warning_type": "Dynamic Render Path",
-      "warning_code": 15,
-      "fingerprint": "3b0a20b08aef13cf8cf865384fae0cfd3324d8200a83262bf4abbc8091b5fec5",
-      "check_name": "Render",
-      "message": "Render path contains parameter value",
-      "file": "app/views/admin/custom_emojis/index.html.haml",
-      "line": 31,
-      "link": "http://brakemanscanner.org/docs/warning_types/dynamic_render_path/",
-      "code": "render(action => filtered_custom_emojis.page(params[:page]), {})",
-      "render_path": [{"type":"controller","class":"Admin::CustomEmojisController","method":"index","line":9,"file":"app/controllers/admin/custom_emojis_controller.rb"}],
-      "location": {
-        "type": "template",
-        "template": "admin/custom_emojis/index"
-      },
-      "user_input": "params[:page]",
-      "confidence": "Weak",
-      "note": ""
-    },
     {
       "warning_type": "Dynamic Render Path",
       "warning_code": 15,
@@ -105,7 +86,7 @@
       "line": 131,
       "link": "http://brakemanscanner.org/docs/warning_types/link_to_href",
       "code": "link_to(Account.find(params[:id]).followers_url, Account.find(params[:id]).followers_url)",
-      "render_path": [{"type":"controller","class":"Admin::AccountsController","method":"show","line":13,"file":"app/controllers/admin/accounts_controller.rb"}],
+      "render_path": [{"type":"controller","class":"Admin::AccountsController","method":"show","line":15,"file":"app/controllers/admin/accounts_controller.rb"}],
       "location": {
         "type": "template",
         "template": "admin/accounts/show"
@@ -124,7 +105,7 @@
       "line": 106,
       "link": "http://brakemanscanner.org/docs/warning_types/link_to_href",
       "code": "link_to(Account.find(params[:id]).salmon_url, Account.find(params[:id]).salmon_url)",
-      "render_path": [{"type":"controller","class":"Admin::AccountsController","method":"show","line":13,"file":"app/controllers/admin/accounts_controller.rb"}],
+      "render_path": [{"type":"controller","class":"Admin::AccountsController","method":"show","line":15,"file":"app/controllers/admin/accounts_controller.rb"}],
       "location": {
         "type": "template",
         "template": "admin/accounts/show"
@@ -133,6 +114,25 @@
       "confidence": "Weak",
       "note": ""
     },
+    {
+      "warning_type": "Dynamic Render Path",
+      "warning_code": 15,
+      "fingerprint": "8d843713d99e8403f7992f3e72251b633817cf9076ffcbbad5613859d2bbc127",
+      "check_name": "Render",
+      "message": "Render path contains parameter value",
+      "file": "app/views/admin/custom_emojis/index.html.haml",
+      "line": 31,
+      "link": "http://brakemanscanner.org/docs/warning_types/dynamic_render_path/",
+      "code": "render(action => filtered_custom_emojis.eager_load(:local_counterpart).page(params[:page]), {})",
+      "render_path": [{"type":"controller","class":"Admin::CustomEmojisController","method":"index","line":9,"file":"app/controllers/admin/custom_emojis_controller.rb"}],
+      "location": {
+        "type": "template",
+        "template": "admin/custom_emojis/index"
+      },
+      "user_input": "params[:page]",
+      "confidence": "Weak",
+      "note": ""
+    },
     {
       "warning_type": "SQL Injection",
       "warning_code": 0,
@@ -140,7 +140,7 @@
       "check_name": "SQL",
       "message": "Possible SQL injection",
       "file": "lib/mastodon/snowflake.rb",
-      "line": 86,
+      "line": 87,
       "link": "http://brakemanscanner.org/docs/warning_types/sql_injection/",
       "code": "connection.execute(\"        CREATE OR REPLACE FUNCTION timestamp_id(table_name text)\\n        RETURNS bigint AS\\n        $$\\n          DECLARE\\n            time_part bigint;\\n            sequence_base bigint;\\n            tail bigint;\\n          BEGIN\\n            time_part := (\\n              -- Get the time in milliseconds\\n              ((date_part('epoch', now()) * 1000))::bigint\\n              -- And shift it over two bytes\\n              << 16);\\n\\n            sequence_base := (\\n              'x' ||\\n              -- Take the first two bytes (four hex characters)\\n              substr(\\n                -- Of the MD5 hash of the data we documented\\n                md5(table_name ||\\n                  '#{SecureRandom.hex(16)}' ||\\n                  time_part::text\\n                ),\\n                1, 4\\n              )\\n            -- And turn it into a bigint\\n            )::bit(16)::bigint;\\n\\n            -- Finally, add our sequence number to our base, and chop\\n            -- it to the last two bytes\\n            tail := (\\n              (sequence_base + nextval(table_name || '_id_seq'))\\n              & 65535);\\n\\n            -- Return the time part and the sequence part. OR appears\\n            -- faster here than addition, but they're equivalent:\\n            -- time_part has no trailing two bytes, and tail is only\\n            -- the last two bytes.\\n            RETURN time_part | tail;\\n          END\\n        $$ LANGUAGE plpgsql VOLATILE;\\n\")",
       "render_path": null,
@@ -182,7 +182,7 @@
       "line": 95,
       "link": "http://brakemanscanner.org/docs/warning_types/link_to_href",
       "code": "link_to(Account.find(params[:id]).remote_url, Account.find(params[:id]).remote_url)",
-      "render_path": [{"type":"controller","class":"Admin::AccountsController","method":"show","line":13,"file":"app/controllers/admin/accounts_controller.rb"}],
+      "render_path": [{"type":"controller","class":"Admin::AccountsController","method":"show","line":15,"file":"app/controllers/admin/accounts_controller.rb"}],
       "location": {
         "type": "template",
         "template": "admin/accounts/show"
@@ -240,7 +240,7 @@
       "line": 125,
       "link": "http://brakemanscanner.org/docs/warning_types/link_to_href",
       "code": "link_to(Account.find(params[:id]).outbox_url, Account.find(params[:id]).outbox_url)",
-      "render_path": [{"type":"controller","class":"Admin::AccountsController","method":"show","line":13,"file":"app/controllers/admin/accounts_controller.rb"}],
+      "render_path": [{"type":"controller","class":"Admin::AccountsController","method":"show","line":15,"file":"app/controllers/admin/accounts_controller.rb"}],
       "location": {
         "type": "template",
         "template": "admin/accounts/show"
@@ -269,6 +269,6 @@
       "note": ""
     }
   ],
-  "updated": "2017-10-07 19:24:02 +0200",
+  "updated": "2017-10-20 00:00:54 +0900",
   "brakeman_version": "4.0.1"
 }
diff --git a/config/locales/en.yml b/config/locales/en.yml
index d72ec92d0bb..ce439029c57 100644
--- a/config/locales/en.yml
+++ b/config/locales/en.yml
@@ -134,6 +134,7 @@ en:
       listed: Listed
       new:
         title: Add new custom emoji
+      overwrite: Overwrite
       shortcode: Shortcode
       shortcode_hint: At least 2 characters, only alphanumeric characters and underscores
       title: Custom emojis