diff --git a/lib/geocoder.rb b/lib/geocoder.rb
index 778c12b9246aac0ce4e2891ef7ba8718e6d64024..5bce2283b9e2463c76edf7ba9e4e99e1bd830ff7 100644
--- a/lib/geocoder.rb
+++ b/lib/geocoder.rb
@@ -106,7 +106,7 @@ module Geocoder
       klass = name.split("_").map{ |i| i[0...1].upcase + i[1..-1] }.join
       Geocoder::Lookup.const_get(klass).new
     else
-      valids = valid_lookups.join(", ")
+      valids = valid_lookups.map(&:inspect).join(", ")
       raise ConfigurationError, "Please specify a valid lookup for Geocoder " +
         "(#{name.inspect} is not one of: #{valids})."
     end