1 files changed, 11 insertions, 0 deletions
diff --git a/app/models/project_services/issue_tracker_service.rb b/app/models/project_services/issue_tracker_service.rb
index 9e65fdbf9d6..50435b67eda 100644
--- a/app/models/project_services/issue_tracker_service.rb
+++ b/app/models/project_services/issue_tracker_service.rb
@@ -1,4 +1,6 @@
 class IssueTrackerService < Service
+  validate :one_issue_tracker, if: :activated?, on: :manual_change
+
   default_value_for :category, 'issue_tracker'
 
   # Pattern used to extract links from comments
@@ -92,4 +94,13 @@ class IssueTrackerService < Service
   def issues_tracker
     Gitlab.config.issues_tracker[to_param]
   end
+
+  def one_issue_tracker
+    return if template?
+    return if project.blank?
+
+    if project.services.external_issue_trackers.where.not(id: id).any?
+      errors.add(:base, 'Another issue tracker is already in use. Only one issue tracker service can be active at a time')
+    end
+  end
 end