diff --git a/lib/redmine/wiki_formatting/macros.rb b/lib/redmine/wiki_formatting/macros.rb
index 731c1bc00..d3a728963 100644
--- a/lib/redmine/wiki_formatting/macros.rb
+++ b/lib/redmine/wiki_formatting/macros.rb
@@ -236,8 +236,11 @@ module Redmine
         size = nil unless size > 0
         if obj && obj.respond_to?(:attachments) && attachment = Attachment.latest_attach(obj.attachments, filename)
           title = options[:title] || attachment.title
-          img = image_tag(url_for(:controller => 'attachments', :action => 'thumbnail', :id => attachment, :size => size), :alt => attachment.filename)
-          link_to(img, url_for(:controller => 'attachments', :action => 'show', :id => attachment), :class => 'thumbnail', :title => title)
+          thumbnail_url = url_for(:controller => 'attachments', :action => 'thumbnail', :id => attachment, :size => size, :only_path => false)
+          image_url = url_for(:controller => 'attachments', :action => 'show', :id => attachment, :only_path => false)
+
+          img = image_tag(thumbnail_url, :alt => attachment.filename)
+          link_to(img, image_url, :class => 'thumbnail', :title => title)
         else
           raise "Attachment #{filename} not found"
         end
diff --git a/test/unit/lib/redmine/wiki_formatting/macros_test.rb b/test/unit/lib/redmine/wiki_formatting/macros_test.rb
index da0094c0b..443b6f4d8 100644
--- a/test/unit/lib/redmine/wiki_formatting/macros_test.rb
+++ b/test/unit/lib/redmine/wiki_formatting/macros_test.rb
@@ -302,8 +302,8 @@ RAW
   end
 
   def test_macro_thumbnail
-    link = link_to('<img alt="testfile.PNG" src="/attachments/thumbnail/17" />'.html_safe,
-                   "/attachments/17",
+    link = link_to('<img alt="testfile.PNG" src="http://test.host/attachments/thumbnail/17" />'.html_safe,
+                   "http://test.host/attachments/17",
                    :class => "thumbnail",
                    :title => "testfile.PNG")
     assert_equal "<p>#{link}</p>",
@@ -311,8 +311,8 @@ RAW
   end
 
   def test_macro_thumbnail_with_size
-    link = link_to('<img alt="testfile.PNG" src="/attachments/thumbnail/17/200" />'.html_safe,
-                   "/attachments/17",
+    link = link_to('<img alt="testfile.PNG" src="http://test.host/attachments/thumbnail/17/200" />'.html_safe,
+                   "http://test.host/attachments/17",
                    :class => "thumbnail",
                    :title => "testfile.PNG")
     assert_equal "<p>#{link}</p>",
@@ -320,8 +320,8 @@ RAW
   end
 
   def test_macro_thumbnail_with_title
-    link = link_to('<img alt="testfile.PNG" src="/attachments/thumbnail/17" />'.html_safe,
-                   "/attachments/17",
+    link = link_to('<img alt="testfile.PNG" src="http://test.host/attachments/thumbnail/17" />'.html_safe,
+                   "http://test.host/attachments/17",
                    :class => "thumbnail",
                    :title => "Cool image")
     assert_equal "<p>#{link}</p>",