Properly link to the right issue or merge request

app/helpers/application_helper.rb

@@ -293,6 +293,26 @@ module ApplicationHelper
     end
   end
+  def issuable_link_next(project,issuable)
+    if project.nil?
+      nil
+    elsif current_controller?(:issues)
+      namespace_project_issue_path(project.namespace, project, next_issuable_for(project, issuable.id).try(:iid))
+    elsif current_controller?(:merge_requests)
+      namespace_project_merge_request_path(project.namespace, project, next_issuable_for(project, issuable.id).try(:iid))
+    end
+  end
+
+  def issuable_link_prev(project,issuable)
+    if project.nil?
+      nil
+    elsif current_controller?(:issues)
+      namespace_project_issue_path(project.namespace, project, prev_issuable_for(project, issuable.id).try(:iid))
+    elsif current_controller?(:merge_requests)
+      namespace_project_merge_request_path(project.namespace, project, prev_issuable_for(project, issuable.id).try(:iid))
+    end
+  end
+
   def issuable_count(entity, project)
     if project.nil?
       0

app/views/shared/issuable/_sidebar.html.haml

@@ -13,12 +13,12 @@
             = icon('angle-double-right')
       .issuable-nav.pull-right.btn-group{role: 'group', "aria-label" => '...'}
         - if has_prev_issuable?(@project, issuable.id)
-          = link_to 'Prev', namespace_project_issue_path(@project.namespace, @project, prev_issuable_for(@project, issuable.id).try(:iid)), class: 'btn btn-default'
+          = link_to 'Prev', issuable_link_prev(@project, issuable), class: 'btn btn-default'
         - else
           %a.btn.btn-default.disabled{href: '#'}
             Prev
         - if has_next_issuable?(@project, issuable.id)
-          = link_to 'Next', namespace_project_issue_path(@project.namespace, @project, next_issuable_for(@project, issuable.id).try(:iid)), class: 'btn btn-default'
+          = link_to 'Next', issuable_link_next(@project, issuable), class: 'btn btn-default'
         - else
           %a.btn.btn-default.disabled{href: '#'}
             Next