diff --git a/Gemfile b/Gemfile
index d2b5cae..a171db6 100644
--- a/Gemfile
+++ b/Gemfile
@@ -11,6 +11,9 @@ gemspec
 # checkout the latest version (develop) from github.
 allow_local = ENV['FAVOR_LOCAL_GEMS']
 
+gem 'regexp_parser', "2.9.0"
+# pin regexp_parser to 2.9.0, for more information: https://github.com/NREL/OpenStudio/issues/5203
+
 # pin this dependency to avoid unicode_normalize error
 # gem 'addressable', '2.8.1'
 # pin this dependency to avoid using racc dependency (which has native extensions)
@@ -27,5 +30,5 @@ gem 'openstudio-extension', '~> 0.8.1'
 # if allow_local && File.exist?('../urbanopt-core-gem')
 #   gem 'urbanopt-core', path: '../urbanopt-core-gem'
 # elsif allow_local
-gem 'urbanopt-core', github: 'URBANopt/urbanopt-core-gem', branch: 'os38'
+gem 'urbanopt-core', github: 'urbanopt/urbanopt-core-gem', branch: 'os38'
 # end