Adds a reference to GoogleAuth
diff --git a/src/ruby/grpc.gemspec b/src/ruby/grpc.gemspec
index bc59c23..25a3ff5 100755
--- a/src/ruby/grpc.gemspec
+++ b/src/ruby/grpc.gemspec
@@ -22,6 +22,7 @@
 
   s.add_dependency 'faraday', '~> 0.9'
   s.add_dependency 'google-protobuf', '~> 3.0.0alpha.1.1'
+  s.add_dependency 'googleauth', '~> 0.1'
   s.add_dependency 'logging', '~> 1.8'
   s.add_dependency 'jwt', '~> 1.2.1'
   s.add_dependency 'minitest', '~> 5.4'  # reqd for interop tests