diff --git a/CHANGELOG b/CHANGELOG
index 2056b5e7b3..545a9f66b9 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,6 +1,7 @@
 Please view this file on the master branch, on stable branches it's out of date.
 
 v 8.9.5
+  - Fix diff comments not showing up in activity feed. !5069
   - Add index on both Award Emoji user and name. !5061
   - Downgrade to Redis 3.2.2 due to massive memory leak with Sidekiq. !5056
   - Re-enable import button when import process fails due to namespace already being taken. !5053
diff --git a/app/models/event.rb b/app/models/event.rb
index 716039fb54..199e6aceed 100644
--- a/app/models/event.rb
+++ b/app/models/event.rb
@@ -67,7 +67,7 @@ class Event < ActiveRecord::Base
     elsif issue? || issue_note?
       Ability.abilities.allowed?(user, :read_issue, note? ? note_target : target)
     else
-      ((merge_request? || note?) && target) || milestone?
+      ((merge_request? || note?) && target.present?) || milestone?
     end
   end
 
@@ -136,7 +136,7 @@ class Event < ActiveRecord::Base
   end
 
   def note?
-    target_type == "Note"
+    target.is_a?(Note)
   end
 
   def issue?
diff --git a/spec/models/event_spec.rb b/spec/models/event_spec.rb
index 166a1dc4dd..6ac19756f1 100644
--- a/spec/models/event_spec.rb
+++ b/spec/models/event_spec.rb
@@ -46,6 +46,22 @@ describe Event, models: true do
     it { expect(@event.author).to eq(@user) }
   end
 
+  describe '#note?' do
+    subject { Event.new(project: target.project, target: target) }
+
+    context 'issue note event' do
+      let(:target) { create(:note_on_issue) }
+
+      it { is_expected.to be_note }
+    end
+
+    context 'merge request diff note event' do
+      let(:target) { create(:note_on_merge_request_diff) }
+
+      it { is_expected.to be_note }
+    end
+  end
+
   describe '#visible_to_user?' do
     let(:project) { create(:empty_project, :public) }
     let(:non_member) { create(:user) }
@@ -89,7 +105,7 @@ describe Event, models: true do
       end
     end
 
-    context 'note event' do
+    context 'issue note event' do
       context 'on non confidential issues' do
         let(:target) { note_on_issue }
 
@@ -112,6 +128,20 @@ describe Event, models: true do
         it { expect(event.visible_to_user?(admin)).to eq true }
       end
     end
+
+    context 'merge request diff note event' do
+      let(:project) { create(:project, :public) }
+      let(:merge_request) { create(:merge_request, source_project: project, author: author, assignee: assignee) }
+      let(:note_on_merge_request) { create(:note_on_merge_request_diff, noteable: merge_request, project: project) }
+      let(:target) { note_on_merge_request }
+
+      it { expect(event.visible_to_user?(non_member)).to eq true }
+      it { expect(event.visible_to_user?(author)).to eq true }
+      it { expect(event.visible_to_user?(assignee)).to eq true }
+      it { expect(event.visible_to_user?(member)).to eq true }
+      it { expect(event.visible_to_user?(guest)).to eq true }
+      it { expect(event.visible_to_user?(admin)).to eq true }
+    end
   end
 
   describe '.limit_recent' do