diff --git a/lib/banzai/filter/issue_reference_filter.rb b/lib/banzai/filter/issue_reference_filter.rb
index 2614261f9eb..5351272f42d 100644
--- a/lib/banzai/filter/issue_reference_filter.rb
+++ b/lib/banzai/filter/issue_reference_filter.rb
@@ -31,10 +31,14 @@ module Banzai
           projects_per_reference.each do |path, project|
             issue_ids = references_per_project[path]
 
-            next unless project.default_issues_tracker?
+            if project.default_issues_tracker?
+              issues = project.issues.where(iid: issue_ids.to_a)
+            else
+              issues = issue_ids.map { |id| ExternalIssue.new(id, project) }
+            end
 
-            project.issues.where(iid: issue_ids.to_a).each do |issue|
-              hash[project][issue.iid] = issue
+            issues.each do |issue|
+              hash[project][issue.iid.to_i] = issue
             end
           end
 
diff --git a/spec/lib/banzai/filter/issue_reference_filter_spec.rb b/spec/lib/banzai/filter/issue_reference_filter_spec.rb
index 5b63c946114..8d6ce114aa9 100644
--- a/spec/lib/banzai/filter/issue_reference_filter_spec.rb
+++ b/spec/lib/banzai/filter/issue_reference_filter_spec.rb
@@ -198,4 +198,40 @@ describe Banzai::Filter::IssueReferenceFilter, lib: true do
       expect(doc.to_html).to match(/\(<a.+>Reference<\/a>\.\)/)
     end
   end
+
+  describe '#issues_per_Project' do
+    context 'using an internal issue tracker' do
+      it 'returns a Hash containing the issues per project' do
+        doc = Nokogiri::HTML.fragment('')
+        filter = described_class.new(doc, project: project)
+
+        expect(filter).to receive(:projects_per_reference).
+          and_return({ project.path_with_namespace => project })
+
+        expect(filter).to receive(:references_per_project).
+          and_return({ project.path_with_namespace => Set.new([issue.iid]) })
+
+        expect(filter.issues_per_project).
+          to eq({ project => { issue.iid => issue } })
+      end
+    end
+
+    context 'using an external issue tracker' do
+      it 'returns a Hash containing the issues per project' do
+        doc = Nokogiri::HTML.fragment('')
+        filter = described_class.new(doc, project: project)
+
+        expect(project).to receive(:default_issues_tracker?).and_return(false)
+
+        expect(filter).to receive(:projects_per_reference).
+          and_return({ project.path_with_namespace => project })
+
+        expect(filter).to receive(:references_per_project).
+          and_return({ project.path_with_namespace => Set.new([1]) })
+
+        expect(filter.issues_per_project[project][1]).
+          to be_an_instance_of(ExternalIssue)
+      end
+    end
+  end
 end