diff --git a/src/app/atom-theme.coffee b/src/app/atom-theme.coffee
index b52ed3111..dc3d3d473 100644
--- a/src/app/atom-theme.coffee
+++ b/src/app/atom-theme.coffee
@@ -11,8 +11,7 @@ class AtomTheme extends Theme
     if /\.css$/.test(@path)
       @loadStylesheet @path
     else
-      json = fs.read(fs.join(@path, "package.json"))
-      for stylesheetName in JSON.parse(json).stylesheets
-        stylesheetPath = fs.join(@path, stylesheetName)
-        @loadStylesheet stylesheetPath
+      metadataPath = fs.resolveExtension(fs.join(@path, 'package'), ['cson', 'json'])
+      stylesheetNames = fs.readObject(metadataPath).stylesheets
+      @loadStylesheet(fs.join(@path, name)) for name in stylesheetNames
     super
diff --git a/themes/atom-dark-ui/package.cson b/themes/atom-dark-ui/package.cson
new file mode 100644
index 000000000..53831688d
--- /dev/null
+++ b/themes/atom-dark-ui/package.cson
@@ -0,0 +1,11 @@
+'stylesheets': [
+  'atom.css'
+  'editor.css'
+  'select-list.css'
+  'tree-view.css'
+  'tabs.css'
+  'status-bar.css'
+  'command-panel.css'
+  'command-logger.css'
+  'blurred.css'
+]
diff --git a/themes/atom-dark-ui/package.json b/themes/atom-dark-ui/package.json
deleted file mode 100644
index 7561f6327..000000000
--- a/themes/atom-dark-ui/package.json
+++ /dev/null
@@ -1,13 +0,0 @@
-{
-  "stylesheets":[
-    "atom.css",
-    "editor.css",
-    "select-list.css",
-    "tree-view.css",
-    "tabs.css",
-    "status-bar.css",
-    "command-panel.css",
-    "command-logger.css",
-    "blurred.css"
-  ]
-}
diff --git a/themes/atom-light-ui/package.cson b/themes/atom-light-ui/package.cson
new file mode 100644
index 000000000..53831688d
--- /dev/null
+++ b/themes/atom-light-ui/package.cson
@@ -0,0 +1,11 @@
+'stylesheets': [
+  'atom.css'
+  'editor.css'
+  'select-list.css'
+  'tree-view.css'
+  'tabs.css'
+  'status-bar.css'
+  'command-panel.css'
+  'command-logger.css'
+  'blurred.css'
+]
diff --git a/themes/atom-light-ui/package.json b/themes/atom-light-ui/package.json
deleted file mode 100644
index 7561f6327..000000000
--- a/themes/atom-light-ui/package.json
+++ /dev/null
@@ -1,13 +0,0 @@
-{
-  "stylesheets":[
-    "atom.css",
-    "editor.css",
-    "select-list.css",
-    "tree-view.css",
-    "tabs.css",
-    "status-bar.css",
-    "command-panel.css",
-    "command-logger.css",
-    "blurred.css"
-  ]
-}