diff --git a/app/models/commit.rb b/app/models/commit.rb
index 2c244fc0410f959c409535bc9b14318ca529a8b7..f02fe240540a288ad15c9cbeb1b83f65dc1bb466 100644
--- a/app/models/commit.rb
+++ b/app/models/commit.rb
@@ -72,7 +72,10 @@ class Commit
   #
   # This pattern supports cross-project references.
   def self.reference_pattern
-    %r{(?:#{Project.reference_pattern}#{reference_prefix})?(?<commit>\h{6,40})}
+    %r{
+      (?:#{Project.reference_pattern}#{reference_prefix})?
+      (?<commit>\h{6,40})
+    }x
   end
 
   def to_reference(from_project = nil)
diff --git a/app/models/issue.rb b/app/models/issue.rb
index ea6b9329b07431592de768a2c9a916fb4f62ada6..2456b7d0dc14506572d7d869a7fecdb9fe8f9221 100644
--- a/app/models/issue.rb
+++ b/app/models/issue.rb
@@ -63,7 +63,7 @@ class Issue < ActiveRecord::Base
   # This pattern supports cross-project references.
   def self.reference_pattern
     %r{
-      #{Project.reference_pattern}?
+      (#{Project.reference_pattern})?
       #{Regexp.escape(reference_prefix)}(?<issue>\d+)
     }x
   end
diff --git a/app/models/merge_request.rb b/app/models/merge_request.rb
index 6c90d09b8662adfa83481393384c455aa9a14b92..c57016dd6a22f6cb88fc2a12a76090f5a47ac35c 100644
--- a/app/models/merge_request.rb
+++ b/app/models/merge_request.rb
@@ -145,7 +145,7 @@ class MergeRequest < ActiveRecord::Base
   # This pattern supports cross-project references.
   def self.reference_pattern
     %r{
-      #{Project.reference_pattern}?
+      (#{Project.reference_pattern})?
       #{Regexp.escape(reference_prefix)}(?<merge_request>\d+)
     }x
   end
diff --git a/app/models/snippet.rb b/app/models/snippet.rb
index d1619071f4908f6defa8845c7fe063ee0de2693b..3ab9e834c638e7cf90e0ef259b6878cdfa09ec26 100644
--- a/app/models/snippet.rb
+++ b/app/models/snippet.rb
@@ -61,7 +61,7 @@ class Snippet < ActiveRecord::Base
   # This pattern supports cross-project references.
   def self.reference_pattern
     %r{
-      #{Project.reference_pattern}?
+      (#{Project.reference_pattern})?
       #{Regexp.escape(reference_prefix)}(?<snippet>\d+)
     }x
   end