diff --git a/app/logical/sources/strategies/tumblr.rb b/app/logical/sources/strategies/tumblr.rb
index d8ae683fe..8a7d9e7e9 100644
--- a/app/logical/sources/strategies/tumblr.rb
+++ b/app/logical/sources/strategies/tumblr.rb
@@ -113,6 +113,7 @@ module Sources::Strategies
 
     module ApiMethods
       def client
+        raise NotImplementedError.new("Tumblr support is not available (API key not configured).") if Danbooru.config.tumblr_consumer_key.nil?
         ::TumblrApiClient.new(Danbooru.config.tumblr_consumer_key)
       end