diff --git a/lib/gitlab/closing_issue_extractor.rb b/lib/gitlab/closing_issue_extractor.rb
index 9bef9037ad6..58f86abc5c4 100644
--- a/lib/gitlab/closing_issue_extractor.rb
+++ b/lib/gitlab/closing_issue_extractor.rb
@@ -22,7 +22,9 @@ module Gitlab
 
       @extractor.analyze(closing_statements.join(" "))
 
-      @extractor.issues
+      @extractor.issues.reject do |issue|
+        @extractor.project.forked_from?(issue.project) # Don't extract issues on original project
+      end
     end
   end
 end
diff --git a/spec/lib/gitlab/closing_issue_extractor_spec.rb b/spec/lib/gitlab/closing_issue_extractor_spec.rb
index e9b8ce6b5bb..de3f64249a2 100644
--- a/spec/lib/gitlab/closing_issue_extractor_spec.rb
+++ b/spec/lib/gitlab/closing_issue_extractor_spec.rb
@@ -3,10 +3,12 @@ require 'spec_helper'
 describe Gitlab::ClosingIssueExtractor, lib: true do
   let(:project)   { create(:project) }
   let(:project2)   { create(:project) }
+  let(:forked_project) { Projects::ForkService.new(project, project.creator).execute }
   let(:issue)     { create(:issue, project: project) }
   let(:issue2)     { create(:issue, project: project2) }
   let(:reference) { issue.to_reference }
   let(:cross_reference) { issue2.to_reference(project) }
+  let(:fork_cross_reference) { issue.to_reference(forked_project) }
 
   subject { described_class.new(project, project.creator) }
 
@@ -278,6 +280,15 @@ describe Gitlab::ClosingIssueExtractor, lib: true do
       end
     end
 
+    context "with a cross-project fork reference" do
+      subject { described_class.new(forked_project, forked_project.creator) }
+
+      it do
+        message = "Closes #{fork_cross_reference}"
+        expect(subject.closed_by_message(message)).to be_empty
+      end
+    end
+
     context "with an invalid URL" do
       it do
         message = "Closes https://google.com#{urls.namespace_project_issue_path(issue2.project.namespace, issue2.project, issue2)}"