diff --git a/jekyll.gemspec b/jekyll.gemspec
index b4d3483f..53882996 100644
--- a/jekyll.gemspec
+++ b/jekyll.gemspec
@@ -25,7 +25,7 @@ Gem::Specification.new do |s|
 
   s.add_runtime_dependency('liquid', "~> 2.5.2")
   s.add_runtime_dependency('classifier', "~> 1.3")
-  s.add_runtime_dependency('listen', "~> 1.3.0")
+  s.add_runtime_dependency('listen', "~> 1.3")
   s.add_runtime_dependency('maruku', "~> 0.6.0")
   s.add_runtime_dependency('pygments.rb', "~> 0.5.0")
   s.add_runtime_dependency('commander', "~> 4.1.3")
@@ -46,6 +46,7 @@ Gem::Specification.new do |s|
   s.add_development_dependency('simplecov', "~> 0.7")
   s.add_development_dependency('simplecov-gem-adapter', "~> 1.0.1")
   s.add_development_dependency('coveralls', "~> 0.7.0")
+  s.add_development_dependency('mime-types', "~> 1.5")
   s.add_development_dependency('activesupport', '~> 3.2.13')
   s.add_development_dependency('jekyll_test_plugin')
 
diff --git a/lib/jekyll/commands/build.rb b/lib/jekyll/commands/build.rb
index 56fe90e6..5948dd89 100644
--- a/lib/jekyll/commands/build.rb
+++ b/lib/jekyll/commands/build.rb
@@ -37,9 +37,8 @@ module Jekyll
         destination = options['destination']
 
         begin
-          ignored = Regexp.new(Regexp.escape(Pathname.new(destination)
-                                 .relative_path_from(Pathname.new(source))
-                                 .to_path))
+          dest = Pathname.new(destination).relative_path_from(Pathname.new(source)).to_path
+          ignored = Regexp.new(Regexp.escape(dest))
         rescue ArgumentError
           # Destination is outside the source, no need to ignore it.
           ignored = nil
@@ -47,7 +46,7 @@ module Jekyll
 
         Jekyll.logger.info "Auto-regeneration:", "enabled"
 
-        listener = Listen.to(source, ignore: ignored) do |modified, added, removed|
+        listener = Listen.to(source, :ignore => ignored) do |modified, added, removed|
           t = Time.now.strftime("%Y-%m-%d %H:%M:%S")
           n = modified.length + added.length + removed.length
           print Jekyll.logger.formatted_topic("Regenerating:") + "#{n} files at #{t} "