diff --git a/app/assets/javascripts/discourse/models/composer.js.es6 b/app/assets/javascripts/discourse/models/composer.js.es6
index aae9a31055f..2ebbd8b1a67 100644
--- a/app/assets/javascripts/discourse/models/composer.js.es6
+++ b/app/assets/javascripts/discourse/models/composer.js.es6
@@ -977,6 +977,7 @@ const Composer = RestModel.extend({
 
     const data = {
       reply: this.get("reply"),
+      originalText: this.get("originalText"),
       action: this.get("action"),
       title: this.get("title"),
       categoryId: this.get("categoryId"),
@@ -991,22 +992,35 @@ const Composer = RestModel.extend({
       noBump: this.get("noBump")
     };
 
-    this.set("draftStatus", I18n.t("composer.saving_draft_tip"));
-
-    const composer = this;
+    this.setProperties({
+      draftStatus: I18n.t("composer.saving_draft_tip"),
+      draftConflictUser: null
+    });
 
     if (this._clearingStatus) {
       Em.run.cancel(this._clearingStatus);
       this._clearingStatus = null;
     }
 
-    // try to save the draft
     return Draft.save(this.get("draftKey"), this.get("draftSequence"), data)
-      .then(function() {
-        composer.set("draftStatus", I18n.t("composer.saved_draft_tip"));
+      .then(result => {
+        if (result.conflict_user) {
+          this.setProperties({
+            draftStatus: I18n.t("composer.edit_conflict"),
+            draftConflictUser: result.conflict_user
+          });
+        } else {
+          this.setProperties({
+            draftStatus: I18n.t("composer.saved_draft_tip"),
+            draftConflictUser: null
+          });
+        }
       })
-      .catch(function() {
-        composer.set("draftStatus", I18n.t("composer.drafts_offline"));
+      .catch(() => {
+        this.setProperties({
+          draftStatus: I18n.t("composer.drafts_offline"),
+          draftConflictUser: null
+        });
       });
   },
 
@@ -1019,6 +1033,7 @@ const Composer = RestModel.extend({
         this,
         function() {
           self.set("draftStatus", null);
+          self.set("draftConflictUser", null);
           self._clearingStatus = null;
         },
         1000
diff --git a/app/assets/javascripts/discourse/models/draft.js.es6 b/app/assets/javascripts/discourse/models/draft.js.es6
index 86a912f37d8..2f92256ca66 100644
--- a/app/assets/javascripts/discourse/models/draft.js.es6
+++ b/app/assets/javascripts/discourse/models/draft.js.es6
@@ -25,13 +25,15 @@ Draft.reopenClass({
   },
 
   save(key, sequence, data) {
-    data = typeof data === "string" ? data : JSON.stringify(data);
+    const dataJson = typeof data === "string" ? dataJson : JSON.stringify(data);
     return ajax("/draft.json", {
       type: "POST",
       data: {
         draft_key: key,
-        data: data,
-        sequence: sequence
+        data: dataJson,
+        sequence,
+        post_id: data.postId,
+        original_text: data.originalText
       }
     });
   }
diff --git a/app/assets/javascripts/discourse/templates/composer.hbs b/app/assets/javascripts/discourse/templates/composer.hbs
index d60ed2e804d..f3e50c7561c 100644
--- a/app/assets/javascripts/discourse/templates/composer.hbs
+++ b/app/assets/javascripts/discourse/templates/composer.hbs
@@ -149,6 +149,9 @@
                 </div>
               {{/if}}
               <div id='draft-status' class="{{if isUploading 'hidden'}}">
+                {{#if model.draftConflictUser}}
+                  {{avatar model.draftConflictUser imageSize="small"}}
+                {{/if}}
                 {{model.draftStatus}}
               </div>
             </div>
diff --git a/app/controllers/draft_controller.rb b/app/controllers/draft_controller.rb
index ebd0dd1bccb..9491c833e2a 100644
--- a/app/controllers/draft_controller.rb
+++ b/app/controllers/draft_controller.rb
@@ -10,6 +10,15 @@ class DraftController < ApplicationController
 
   def update
     Draft.set(current_user, params[:draft_key], params[:sequence].to_i, params[:data])
+
+    if params[:post_id] && params[:original_text]
+      post = Post.find_by(id: params[:post_id])
+      if post && post.raw != params[:original_text]
+        conflict_user = BasicUserSerializer.new(post.last_editor, root: false)
+        return render json: success_json.merge(conflict_user: conflict_user)
+      end
+    end
+
     render json: success_json
   end
 
diff --git a/config/locales/client.en.yml b/config/locales/client.en.yml
index 47658fd6c9b..9760176d738 100644
--- a/config/locales/client.en.yml
+++ b/config/locales/client.en.yml
@@ -1356,6 +1356,7 @@ en:
       saved_local_draft_tip: "saved locally"
       similar_topics: "Your topic is similar to..."
       drafts_offline: "drafts offline"
+      edit_conflict: 'edit conflict'
 
       group_mentioned_limit: "<b>Warning!</b> You mentioned <a href='{{group_link}}'>{{group}}</a>, however this group has more members than the administrator configured mention limit of {{max}} users. Nobody will be notified. "
       group_mentioned:
diff --git a/spec/requests/draft_controller_spec.rb b/spec/requests/draft_controller_spec.rb
index 55f471a44d3..0c66de5ee46 100644
--- a/spec/requests/draft_controller_spec.rb
+++ b/spec/requests/draft_controller_spec.rb
@@ -13,6 +13,34 @@ describe DraftController do
     expect(Draft.get(user, 'xyz', 0)).to eq('my data')
   end
 
+  it 'checks for an conflict on update' do
+    user = sign_in(Fabricate(:user))
+    post = Fabricate(:post, user: user)
+
+    post "/draft.json", params: {
+      username: user.username,
+      draft_key: "topic",
+      sequence: 0,
+      data: "{}",
+      post_id: post.id,
+      original_text: post.raw
+    }
+
+    expect(JSON.parse(response.body)['conflict_user']).to eq(nil)
+
+    post "/draft.json", params: {
+      username: user.username,
+      draft_key: "topic",
+      sequence: 0,
+      data: "{}",
+      post_id: post.id,
+      original_text: "something else"
+    }
+
+    expect(JSON.parse(response.body)['conflict_user']['id']).to eq(post.last_editor.id)
+    expect(JSON.parse(response.body)['conflict_user']).to include('avatar_template')
+  end
+
   it 'destroys drafts when required' do
     user = sign_in(Fabricate(:user))
     Draft.set(user, 'xxx', 0, 'hi')