diff --git a/lib/banzai/filter/gollum_tags_filter.rb b/lib/banzai/filter/gollum_tags_filter.rb
index f78b30bd4e9..e4a73030597 100644
--- a/lib/banzai/filter/gollum_tags_filter.rb
+++ b/lib/banzai/filter/gollum_tags_filter.rb
@@ -14,7 +14,10 @@ module Banzai
       include ActionView::Helpers::TagHelper
 
       # Pattern to match tag contents.
-      TAGS_PATTERN = %r{(.?)\[\[(.+?)\]\]([^\[]?)}
+      TAGS_PATTERN = %r{\[\[(.+?)\]\]}
+
+      # Pattern to match allowed image extensions
+      ALLOWED_IMAGE_EXTENSIONS = %r{.+(jpg|png|gif|svg|bmp)\z}i
 
       def call
         search_text_nodes(doc).each do |node|
@@ -22,9 +25,11 @@ module Banzai
 
           next unless content.match(TAGS_PATTERN)
 
-          html = process_tag($2)
+          html = process_tag($1)
 
-          node.replace(html) if html != node.content
+          if html && html != node.content
+            node.replace(html)
+          end
         end
 
         doc
@@ -38,11 +43,11 @@ module Banzai
       #
       # Returns the String HTML version of the tag.
       def process_tag(tag)
-        if html = process_image_tag(tag)
-          html
-        else
-          process_page_link_tag(tag)
-        end
+        parts = tag.split('|')
+
+        return if parts.size.zero?
+
+        process_image_tag(parts) || process_page_link_tag(parts)
       end
 
       # Attempt to process the tag as an image tag.
@@ -51,16 +56,15 @@ module Banzai
       #
       # Returns the String HTML if the tag is a valid image tag or nil
       # if it is not.
-      def process_image_tag(tag)
-        parts = tag.split('|')
-        return if parts.size.zero?
+      def process_image_tag(parts)
+        content = parts[0].strip
 
-        name = parts[0].strip
+        return unless image?(content)
 
-        if file = project_wiki.find_file(name)
+        if url?(content)
+          path = content
+        elsif file = project_wiki.find_file(content)
           path = ::File.join project_wiki_base_path, file.path
-        elsif name =~ /^https?:\/\/.+(jpg|png|gif|svg|bmp)$/i
-          path = name
         end
 
         if path
@@ -68,16 +72,21 @@ module Banzai
         end
       end
 
+      def image?(path)
+        path =~ ALLOWED_IMAGE_EXTENSIONS
+      end
+
+      def url?(path)
+        path.start_with?(*%w(http https))
+      end
+
       # Attempt to process the tag as a page link tag.
       #
       # tag - The String tag contents (the stuff inside the double brackets).
       #
       # Returns the String HTML if the tag is a valid page link tag or nil
       # if it is not.
-      def process_page_link_tag(tag)
-        parts = tag.split('|')
-        return if parts.size.zero?
-
+      def process_page_link_tag(parts)
         if parts.size == 1
           url = parts[0].strip
         else
diff --git a/spec/lib/banzai/filter/gollum_tags_filter_spec.rb b/spec/lib/banzai/filter/gollum_tags_filter_spec.rb
index 530b37526b3..38baa819957 100644
--- a/spec/lib/banzai/filter/gollum_tags_filter_spec.rb
+++ b/spec/lib/banzai/filter/gollum_tags_filter_spec.rb
@@ -37,8 +37,6 @@ describe Banzai::Filter::GollumTagsFilter, lib: true do
 
   context 'linking external images' do
     it 'creates img tag for valid URL' do
-      expect(project_wiki).to receive(:find_file).with('http://example.com/image.jpg').and_return(nil)
-
       tag = '[[http://example.com/image.jpg]]'
       doc = filter("See #{tag}", project_wiki: project_wiki)
 
@@ -46,8 +44,6 @@ describe Banzai::Filter::GollumTagsFilter, lib: true do
     end
 
     it 'does not creates img tag for invalid URL' do
-      expect(project_wiki).to receive(:find_file).with('http://example.com/image.pdf').and_return(nil)
-
       tag = '[[http://example.com/image.pdf]]'
       doc = filter("See #{tag}", project_wiki: project_wiki)