diff --git a/src/theme-package.coffee b/src/theme-package.coffee
index f90ca1524..ca15ed178 100644
--- a/src/theme-package.coffee
+++ b/src/theme-package.coffee
@@ -11,7 +11,7 @@ class ThemePackage extends AtomPackage
   getStylesheetType: -> 'theme'
 
   enable: ->
-    themes = atom.config.get('core.themes')
+    themes = atom.config.get('core.themes') ? []
     themes.unshift(@metadata.name)
     atom.config.set('core.themes', themes)