diff --git a/CHANGELOG b/CHANGELOG
index d5b05125110873897741e28d5a6135b31800aadf..3f9af5b9f9f8ae805d8fb7e36760f8b6491e8223 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -11,6 +11,7 @@ v 7.9.0 (unreleased)
   - Fix ordering of imported but unchanged projects (Marco Wessel)
   - Mobile UI improvements: make aside content expandable
   - Generalize image upload in drag and drop in markdown to all files (Hannes Rosenögger)
+  - Fix mass-unassignment of issues (Robert Speicher)
 
 v 7.8.1
   - Fix run of custom post receive hooks
diff --git a/app/assets/javascripts/project_users_select.js.coffee b/app/assets/javascripts/project_users_select.js.coffee
index 7fb33926096c1b86e3490f7337ed821863b44bd0..885f0d58a6a1861d6b40a77f675db43cbbd4e643 100644
--- a/app/assets/javascripts/project_users_select.js.coffee
+++ b/app/assets/javascripts/project_users_select.js.coffee
@@ -15,7 +15,7 @@ class @ProjectUsersSelect
               name: 'Unassigned',
               avatar: null,
               username: 'none',
-              id: ''
+              id: -1
             }
 
             data.results.unshift(nullUser)
diff --git a/spec/services/issues/bulk_update_context_spec.rb b/spec/services/issues/bulk_update_service_spec.rb
similarity index 76%
rename from spec/services/issues/bulk_update_context_spec.rb
rename to spec/services/issues/bulk_update_service_spec.rb
index eb867f78c5cc290008e426d7a2f55ef7bdc60d23..504213e667fa04c3627ef606fad59ac7443f975b 100644
--- a/spec/services/issues/bulk_update_context_spec.rb
+++ b/spec/services/issues/bulk_update_service_spec.rb
@@ -84,6 +84,25 @@ describe Issues::BulkUpdateService do
       expect(@project.issues.first.assignee).to eq(@new_assignee)
     }
 
+    it 'allows mass-unassigning' do
+      @project.issues.first.update_attribute(:assignee, @new_assignee)
+      expect(@project.issues.first.assignee).not_to be_nil
+
+      @params[:update][:assignee_id] = -1
+
+      Issues::BulkUpdateService.new(@project, @user, @params).execute
+      expect(@project.issues.first.assignee).to be_nil
+    end
+
+    it 'does not unassign when assignee_id is not present' do
+      @project.issues.first.update_attribute(:assignee, @new_assignee)
+      expect(@project.issues.first.assignee).not_to be_nil
+
+      @params[:update][:assignee_id] = ''
+
+      Issues::BulkUpdateService.new(@project, @user, @params).execute
+      expect(@project.issues.first.assignee).not_to be_nil
+    end
   end
 
   describe :update_milestone do