diff --git a/lib/opentok/token_generator.rb b/lib/opentok/token_generator.rb
index 26bdd33..1df22ff 100644
--- a/lib/opentok/token_generator.rb
+++ b/lib/opentok/token_generator.rb
@@ -4,6 +4,7 @@
 require "base64"
 require "addressable/uri"
 require "openssl"
+require "active_support/isolated_execution_state"
 require "active_support/time"
 
 module OpenTok