diff --git a/lib/linguist/mime.rb b/lib/linguist/mime.rb
index 22dd754f..2b2ff690 100644
--- a/lib/linguist/mime.rb
+++ b/lib/linguist/mime.rb
@@ -88,7 +88,7 @@ module Linguist
     # Returns true or false
     def self.binary?(ext_or_mime_type)
       mime_type = lookup_mime_type_for(ext_or_mime_type)
-      mime_type.nil? || mime_type.binary?
+      mime_type ? mime_type.binary? : false
     end
 
     # Internal: Lookup mime type for extension or mime type
diff --git a/lib/linguist/mimes.yml b/lib/linguist/mimes.yml
index 0731c5c9..2a4b3c11 100644
--- a/lib/linguist/mimes.yml
+++ b/lib/linguist/mimes.yml
@@ -49,11 +49,43 @@ application/x-wais-source:
 application/vnd.mozilla.xul+xml:
   binary: false
 
+application/vnd.adobe.air-application-installer-package+zip:
+  binary: true
+  extensions:
+  - air
+
 application/octet-stream:
   binary: true
   extensions:
-  - dmg
+  # TODO: Lookup actual content type for these extensions
+  - a
+  - blend
   - dll
+  - dmg
+  - gem
+  - graffle
+  - ipa
+  - lib
+  - mcz
+  - nib
+  - o
+  - odp
+  - ods
+  - odt
+  - otf
+  - ogv
+  - pfx
+  - pigx
+  - plgx
+  - pptx
+  - psd
+  - sib
+  - so
+  - spl
+  - sqlite3
+  - swc
+  - ucode
+  - xpi
 
 application/java-archive:
   binary: true
@@ -61,6 +93,16 @@ application/java-archive:
   - ear
   - war
 
+application/x-chrome-extension:
+  binary: true
+  extensions:
+  - crx
+
+application/x-debian-package:
+  binary: true
+  extensions:
+  - deb
+
 application/x-shockwave-flash:
   binary: true
   extensions:
@@ -74,3 +116,18 @@ image/jpeg:
 
 image/png:
   attachment: false
+
+image/x-icns:
+  binary: true
+  extensions:
+  - icns
+
+text/cache-manifest:
+  extensions:
+  - manifest
+
+video/quicktime:
+  binary: true
+  extensions:
+  - qt
+  - mov
diff --git a/test/test_blob.rb b/test/test_blob.rb
index a8edda84..24e8001b 100644
--- a/test/test_blob.rb
+++ b/test/test_blob.rb
@@ -25,8 +25,9 @@ class TestBlob < Test::Unit::TestCase
   def test_mime_type
     assert_equal "application/ruby", blob("grit.rb").mime_type
     assert_equal "application/xml", blob("bar.xml").mime_type
-    assert_equal "text/plain", blob("dog.o").mime_type
+    assert_equal "application/octet-stream", blob("dog.o").mime_type
     assert_equal "application/sh", blob("script.sh").mime_type
+    assert_equal "text/plain", blob("README").mime_type
   end
 
   def test_content_type
@@ -35,6 +36,7 @@ class TestBlob < Test::Unit::TestCase
     assert_equal "text/plain; charset=utf-8", blob("bar.xml").content_type
     assert_equal "application/octet-stream", blob("dog.o").content_type
     assert_equal "text/plain; charset=utf-8", blob("script.sh").content_type
+    assert_equal "text/plain; charset=utf-8", blob("README").content_type
   end
 
   def test_disposition
@@ -43,6 +45,7 @@ class TestBlob < Test::Unit::TestCase
     assert_equal "attachment; filename=foo+bar.jar", blob("foo bar.jar").disposition
     assert_equal "inline", blob("foo.txt").disposition
     assert_equal "inline", blob("grit.rb").disposition
+    assert_equal "inline", blob("README").disposition
   end
 
   def test_data
@@ -69,6 +72,7 @@ class TestBlob < Test::Unit::TestCase
     assert blob("linguist.gem").binary?
     assert blob("git.deb").binary?
     assert blob("git.exe").binary?
+    assert !blob("README").binary?
     assert !blob("file.txt").binary?
     assert !blob("foo.rb").binary?
     assert !blob("octocat.png").binary?
@@ -76,8 +80,9 @@ class TestBlob < Test::Unit::TestCase
   end
 
   def test_text
-    assert blob("file.txt").text?
+    assert blob("README").text?
     assert blob("file.json").text?
+    assert blob("file.txt").text?
     assert blob("script.sh").text?
   end
 
@@ -90,10 +95,11 @@ class TestBlob < Test::Unit::TestCase
   end
 
   def test_viewable
+    assert blob("README").viewable?
     assert blob("foo.rb").viewable?
     assert blob("script.pl").viewable?
-    assert !blob("octocat.png").viewable?
     assert !blob("linguist.gem").viewable?
+    assert !blob("octocat.png").viewable?
   end
 
   def test_generated
@@ -210,6 +216,8 @@ class TestBlob < Test::Unit::TestCase
     assert_equal Language['VimL'],  blob(".gvimrc").language
     assert_equal Language['INI'],   blob(".gitconfig").language
     assert_equal Language['YAML'],  blob(".gemrc").language
+
+    assert_equal Language['Text'], blob("README").language
   end
 
   def test_lexer
diff --git a/test/test_mime.rb b/test/test_mime.rb
index 5bbd5dfd..89aa7207 100644
--- a/test/test_mime.rb
+++ b/test/test_mime.rb
@@ -7,6 +7,7 @@ class TestMime < Test::Unit::TestCase
 
   def test_mime
     assert_equal 'text/plain', Mime.mime_for(nil)
+    assert_equal 'text/plain', Mime.mime_for("")
 
     assert_equal 'application/ruby', Mime.mime_for(".rb")
     assert_equal 'application/javascript', Mime.mime_for(".js")
@@ -14,11 +15,19 @@ class TestMime < Test::Unit::TestCase
 
     assert_equal 'text/plain', Mime.mime_for(".kt")
     assert_equal 'text/html', Mime.mime_for(".html")
+    assert_equal 'text/cache-manifest', Mime.mime_for(".manifest")
     assert_equal 'application/sh', Mime.mime_for(".sh")
     assert_equal 'application/latex', Mime.mime_for(".latex")
 
+    assert_equal 'application/vnd.adobe.air-application-installer-package+zip',
+      Mime.mime_for(".air")
     assert_equal 'application/shockwave-flash', Mime.mime_for(".swf")
 
+    assert_equal 'application/chrome-extension', Mime.mime_for(".crx")
+    assert_equal 'application/debian-package', Mime.mime_for(".deb")
+
+    assert_equal 'video/quicktime', Mime.mime_for(".mov")
+
     assert_equal 'application/octet-stream', Mime.mime_for(".dmg")
     assert_equal 'application/octet-stream', Mime.mime_for(".exe")
     assert_equal 'application/octet-stream', Mime.mime_for(".dll")
@@ -30,6 +39,7 @@ class TestMime < Test::Unit::TestCase
 
   def test_content_type
     assert_equal 'text/plain; charset=utf-8', Mime.content_type_for(nil)
+    assert_equal 'text/plain; charset=utf-8', Mime.content_type_for("")
 
     assert_equal 'text/plain; charset=utf-8', Mime.content_type_for(".rb")
     assert_equal 'text/plain; charset=utf-8', Mime.content_type_for(".js")
@@ -40,10 +50,11 @@ class TestMime < Test::Unit::TestCase
     assert_equal 'text/plain; charset=utf-8', Mime.content_type_for(".sh")
     assert_equal 'text/plain; charset=utf-8', Mime.content_type_for(".latex")
 
-    assert_equal 'application/octet-stream', Mime.content_type_for(".swf")
+    assert_equal 'application/octet-stream', Mime.content_type_for(".air")
+    assert_equal 'application/octet-stream', Mime.content_type_for(".dll")
     assert_equal 'application/octet-stream', Mime.content_type_for(".dmg")
     assert_equal 'application/octet-stream', Mime.content_type_for(".exe")
-    assert_equal 'application/octet-stream', Mime.content_type_for(".dll")
+    assert_equal 'application/octet-stream', Mime.content_type_for(".swf")
 
     assert_equal 'application/java-archive', Mime.content_type_for(".jar")
     assert_equal 'application/java-archive', Mime.content_type_for(".ear")
@@ -51,6 +62,9 @@ class TestMime < Test::Unit::TestCase
   end
 
   def test_binary
+    assert !Mime.binary?(nil)
+    assert !Mime.binary?("")
+
     assert Mime.binary?("application/octet-stream")
     assert !Mime.binary?("text/plain")
 
@@ -58,13 +72,12 @@ class TestMime < Test::Unit::TestCase
     assert Mime.binary?("application/ogg")
     assert Mime.binary?("application/pdf")
     assert Mime.binary?("application/x-gzip")
+    assert Mime.binary?("application/x-shockwave-flash")
     assert Mime.binary?("application/zip")
     assert Mime.binary?("audio/mp4")
     assert Mime.binary?("image/gif")
     assert Mime.binary?("image/jpeg")
     assert Mime.binary?("image/png")
-    assert Mime.binary?("java-archive")
-    assert Mime.binary?("x-shockwave-flash")
 
     assert Mime.binary?(".a")
     assert Mime.binary?(".air")