diff --git a/BrainPortal/Gemfile b/BrainPortal/Gemfile
index 95c062d97..311862cef 100644
--- a/BrainPortal/Gemfile
+++ b/BrainPortal/Gemfile
@@ -38,6 +38,7 @@ gem "bcrypt_pbkdf"
 # They are usually the most tricky to compile and integrate into the app.
 gem "rbnacl"
 gem "rbnacl-libsodium"
+gem "psych", '~> 3.3'
 
 # Other utilities
 gem "sys-proctable", '~> 1.2.0'