diff --git a/Gemfile.lock b/Gemfile.lock
index 270e641..51b67a3 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -1,8 +1,9 @@
 PATH
   remote: .
   specs:
-    dummy_dropbox_sdk (0.0.11)
+    dummy_dropbox_sdk (0.0.13)
       dropbox-sdk (>= 1.1)
+      mime-types
 
 GEM
   remote: http://rubygems.org/
@@ -10,6 +11,7 @@ GEM
     dropbox-sdk (1.1)
       json
     json (1.6.1)
+    mime-types (1.18)
 
 PLATFORMS
   ruby
@@ -18,3 +20,4 @@ DEPENDENCIES
   bundler (>= 1.0.0.rc.6)
   dropbox-sdk (>= 1.1)
   dummy_dropbox_sdk!
+  mime-types
diff --git a/dummy_dropbox_sdk.gemspec b/dummy_dropbox_sdk.gemspec
index 21d98f2..de1e0f4 100644
--- a/dummy_dropbox_sdk.gemspec
+++ b/dummy_dropbox_sdk.gemspec
@@ -16,6 +16,7 @@ Gem::Specification.new do |s|
   s.add_development_dependency "bundler", ">= 1.0.0.rc.6"
   
   s.add_dependency "dropbox-sdk", ">= 1.1"
+  s.add_dependency "mime-types"
 
   s.files         = `git ls-files`.split("\n")
   s.test_files    = `git ls-files -- {test,spec,features}/*`.split("\n")