diff --git a/Rakefile b/Rakefile
index 630c02ff..1801ea15 100644
--- a/Rakefile
+++ b/Rakefile
@@ -87,6 +87,13 @@ task :test do
   end
 end
 
+desc "Run specs for all middleman gems"
+task :spec do
+  GEM_PATHS.each do |g|
+    sh "cd #{File.join(ROOT, g)} && #{Gem.ruby} -S rake spec"
+  end
+end
+
 # desc "Rune cane for all middleman gems"
 # task :cane do
 #   GEM_PATHS.each do |g|
@@ -95,4 +102,4 @@ end
 # end
 
 desc "Run tests for all middleman gems"
-task :default => :test
\ No newline at end of file
+task :default => :test
diff --git a/middleman-core/lib/middleman-core/util.rb b/middleman-core/lib/middleman-core/util.rb
index 00a28e2b..0bee9661 100644
--- a/middleman-core/lib/middleman-core/util.rb
+++ b/middleman-core/lib/middleman-core/util.rb
@@ -10,6 +10,9 @@ require "thor"
 # Core Pathname library used for traversal
 require "pathname"
 
+require "tilt"
+require "rack/mime"
+
 module Middleman
 
   module Util
diff --git a/middleman-core/spec/middleman-core/binary_spec.rb b/middleman-core/spec/middleman-core/binary_spec.rb
new file mode 100644
index 00000000..ad04efb7
--- /dev/null
+++ b/middleman-core/spec/middleman-core/binary_spec.rb
@@ -0,0 +1,15 @@
+require 'middleman-core/util'
+
+describe "Middleman::Util#binary?" do
+  %w(plain.txt unicode.txt unicode stars.svgz).each do |file|
+    it "recognizes #{file} as not binary" do
+      Middleman::Util.binary?(File.join(File.dirname(__FILE__), "binary_spec/#{file}")).should be_false
+    end
+  end
+
+  %w(middleman.png middleman).each do |file|
+    it "recognizes #{file} as binary" do
+      Middleman::Util.binary?(File.join(File.dirname(__FILE__), "binary_spec/#{file}")).should be_true
+    end
+  end
+end
diff --git a/middleman-core/spec/middleman-core/binary_spec/middleman b/middleman-core/spec/middleman-core/binary_spec/middleman
new file mode 100644
index 00000000..c685e564
Binary files /dev/null and b/middleman-core/spec/middleman-core/binary_spec/middleman differ
diff --git a/middleman-core/spec/middleman-core/binary_spec/middleman.png b/middleman-core/spec/middleman-core/binary_spec/middleman.png
new file mode 100644
index 00000000..c685e564
Binary files /dev/null and b/middleman-core/spec/middleman-core/binary_spec/middleman.png differ
diff --git a/middleman-core/spec/middleman-core/binary_spec/plain.txt b/middleman-core/spec/middleman-core/binary_spec/plain.txt
new file mode 100644
index 00000000..649adbeb
--- /dev/null
+++ b/middleman-core/spec/middleman-core/binary_spec/plain.txt
@@ -0,0 +1 @@
+Some plain text
diff --git a/middleman-core/spec/middleman-core/binary_spec/stars.svgz b/middleman-core/spec/middleman-core/binary_spec/stars.svgz
new file mode 100644
index 00000000..a54ce7ff
Binary files /dev/null and b/middleman-core/spec/middleman-core/binary_spec/stars.svgz differ
diff --git a/middleman-core/spec/middleman-core/binary_spec/unicode b/middleman-core/spec/middleman-core/binary_spec/unicode
new file mode 100644
index 00000000..13dc1361
--- /dev/null
+++ b/middleman-core/spec/middleman-core/binary_spec/unicode
@@ -0,0 +1 @@
+明日がある。
diff --git a/middleman-core/spec/middleman-core/binary_spec/unicode.txt b/middleman-core/spec/middleman-core/binary_spec/unicode.txt
new file mode 100644
index 00000000..13dc1361
--- /dev/null
+++ b/middleman-core/spec/middleman-core/binary_spec/unicode.txt
@@ -0,0 +1 @@
+明日がある。