diff --git a/lib/csp.js b/lib/csp.js
index 6ab7ea60..c87ca972 100644
--- a/lib/csp.js
+++ b/lib/csp.js
@@ -41,7 +41,7 @@ CspStrategy.computeDirectives = function () {
   mergeDirectives(directives, config.csp.directives)
   mergeDirectivesIf(config.csp.addDefaults, directives, defaultDirectives)
   mergeDirectivesIf(config.useCDN, directives, cdnDirectives)
-  mergeDirectivesIf(config.dropbox.appKey, directives, dropboxDirectives)
+  mergeDirectivesIf(config.dropbox && config.dropbox.appKey, directives, dropboxDirectives)
   mergeDirectivesIf(config.csp.addDisqus, directives, disqusDirectives)
   mergeDirectivesIf(config.csp.addGoogleAnalytics, directives, googleAnalyticsDirectives)
   if (!areAllInlineScriptsAllowed(directives)) {