diff --git a/lib/generators/devise/views_generator.rb b/lib/generators/devise/views_generator.rb
index 4d7bd2ec..fe89b6fe 100644
--- a/lib/generators/devise/views_generator.rb
+++ b/lib/generators/devise/views_generator.rb
@@ -79,23 +79,31 @@ module Devise
       end
 
       def inject_makerb_content
-        if gemfile_exists?
-          append_file gemfile_path, gemfile_content
+        if gemfile
+          append_file gemfile_path, gemfile_content unless gemfile =~ gemfile_content_regexp
         else
           create_file gemfile_path, gemfile_content
         end
       end
 
       def gemfile_path
-        @gemfile_path ||= File.join("Gemfile")
-      end
-
-      def gemfile_exists?
-        File.exists?(File.join(destination_root, gemfile_path))
+        @gemfile_path ||= File.join(destination_root, "Gemfile")
       end
 
       def gemfile_content
-        'gem "markerb"'
+        "gem 'markerb'"
+      end
+
+      def gemfile_content_regexp
+        /gem ['|"]markerb['|"]/
+      end
+
+      def gemfile
+        begin
+          File.read(gemfile_path)
+        rescue
+          nil
+        end
       end
     end
 
diff --git a/test/generators/views_generator_test.rb b/test/generators/views_generator_test.rb
index 80ca671e..39befe15 100644
--- a/test/generators/views_generator_test.rb
+++ b/test/generators/views_generator_test.rb
@@ -34,14 +34,26 @@ class ViewsGeneratorTest < Rails::Generators::TestCase
   end
 
   test "Assert Gemfile got gem markerb injected" do
-    File.open(File.join(destination_root, "Gemfile"), 'w') {|f| f.write("gem 'rails'") }
+    create_gemfile("gem 'rails'")
     run_generator %w(--markerb)
-    assert_file "Gemfile", /gem \"markerb\"/
+    assert_file "Gemfile", /gem 'markerb'/
+    assert_file "Gemfile", /gem 'rails'/
+  end
+
+  test "Assert Gemfile got gem markerb injected only if it does not exist" do
+    gemfile = create_gemfile("gem 'markerb'")
+    run_generator %w(--markerb)
+    assert_equal 1, gemfile.scan("gem 'markerb'").length
   end
 
   test "Assert Gemfile got created with markerb if no gemfile" do
     run_generator %w(--markerb)
-    assert_file "Gemfile", /gem \"markerb\"/
+    assert_file "Gemfile", /gem 'markerb'/
+  end
+
+  def create_gemfile(content=nil)
+    File.open(File.join(destination_root, "Gemfile"), 'w') {|f| f.write(content) }
+    File.read(File.join(destination_root, "Gemfile"))
   end
 
   def assert_files(scope = nil, options={})