diff --git a/.travis.yml b/.travis.yml
index 13518f915..a9844fa4e 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -2,7 +2,7 @@ dist: xenial
 
 language: ruby
 rvm:
-  - 2.4.10
+  - 2.5.9
 env: SECRET_KEY_BASE=859384 RUN_SLOW_TESTS=true
 
 before_install:
diff --git a/Dockerfile b/Dockerfile
index 53effbf6e..47233d314 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,4 +1,4 @@
-FROM ruby:2.4.10
+FROM ruby:2.5.9
 RUN mkdir /morph
 WORKDIR /morph
 # We need a javascript runtime
diff --git a/Gemfile b/Gemfile
index d25c93e54..73521fc13 100644
--- a/Gemfile
+++ b/Gemfile
@@ -94,6 +94,10 @@ gem "validate_url"
 # TODO: Remove this when we can
 gem "nio4r", "~> 2.4.0"
 
+# Adding psych here to lock its version. psych 4.0 causes us issues with installing gems. Ugh.
+# TODO: Remove this as soon as possible
+gem "psych", "< 4.0.0"
+
 group :production do
   # 3.0.0 requires ruby 2.5 or higher.
   # TODO: Remove version lock as soon as we have upgraded to ruby 2.5
diff --git a/Gemfile.lock b/Gemfile.lock
index 3e3ef7df2..da57ef952 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -377,8 +377,7 @@ GEM
     pry-stack_explorer (0.4.13)
       binding_of_caller (~> 0.7)
       pry (~> 0.13)
-    psych (4.0.4)
-      stringio
+    psych (3.3.2)
     public_suffix (4.0.7)
     puma (5.6.4)
       nio4r (~> 2.0)
@@ -436,8 +435,7 @@ GEM
     rb-fsevent (0.11.1)
     rb-inotify (0.10.1)
       ffi (~> 1.0)
-    rdoc (6.4.0)
-      psych (>= 4.0.0)
+    rdoc (6.3.3)
     redcarpet (3.5.1)
     redis (4.5.1)
     regexp_parser (2.5.0)
@@ -555,7 +553,6 @@ GEM
     sshkit (1.21.2)
       net-scp (>= 1.1.2)
       net-ssh (>= 2.8.0)
-    stringio (3.0.2)
     stripe (6.5.0)
     temple (0.8.2)
     thor (1.2.1)
@@ -647,6 +644,7 @@ DEPENDENCIES
   pry-remote
   pry-rescue
   pry-stack_explorer
+  psych (< 4.0.0)
   puma
   rack-livereload
   rack-mini-profiler (< 3.0.0)
diff --git a/README.md b/README.md
index c64d14e1c..a8070c6df 100644
--- a/README.md
+++ b/README.md
@@ -12,7 +12,7 @@
 * Email alerts for broken scrapers
 
 ## Dependencies
-Ruby 2.4.10, Docker, MySQL, SQLite 3, Redis, mitmproxy.
+Ruby 2.5.9, Docker, MySQL, SQLite 3, Redis, mitmproxy.
 (See below for more details about installing Docker)
 
 Development is supported on Linux (Ubuntu 20.04) and Mac OS X.
diff --git a/config/deploy.rb b/config/deploy.rb
index d038709f4..fc3238559 100644
--- a/config/deploy.rb
+++ b/config/deploy.rb
@@ -1,7 +1,7 @@
 set :application, 'morph'
 set :repo_url, 'https://github.com/openaustralia/morph.git'
 
-set :rvm_ruby_version, '2.4.10'
+set :rvm_ruby_version, '2.5.9'
 
 # ask :branch, proc { `git rev-parse --abbrev-ref HEAD`.chomp }
 
diff --git a/provisioning/roles/morph-app/templates/sites/morph.io b/provisioning/roles/morph-app/templates/sites/morph.io
index 54ef77e7b..983f85327 100644
--- a/provisioning/roles/morph-app/templates/sites/morph.io
+++ b/provisioning/roles/morph-app/templates/sites/morph.io
@@ -3,7 +3,7 @@ server {
   server_name {{ server_name }} api.{{ server_name }};
   root /var/www/current/public;
   passenger_enabled on;
-  passenger_ruby /home/deploy/.rvm/gems/ruby-2.4.10/wrappers/ruby;
+  passenger_ruby /home/deploy/.rvm/gems/ruby-2.5.9/wrappers/ruby;
   passenger_max_request_queue_size 300;
 
   # There's a lot of traffic coming to this one scraper. It was putting
diff --git a/provisioning/roles/ruby/handlers/main.yml b/provisioning/roles/ruby/handlers/main.yml
index 39a22cc22..c70d62573 100644
--- a/provisioning/roles/ruby/handlers/main.yml
+++ b/provisioning/roles/ruby/handlers/main.yml
@@ -1,4 +1,4 @@
 ---
-- name: Make ruby-2.4.10 the default
-  command: /bin/sh -l -c 'rvm alias create default ruby-2.4.10'
+- name: Make ruby-2.5.9 the default
+  command: /bin/sh -l -c 'rvm alias create default ruby-2.5.9'
   become_user: deploy
diff --git a/provisioning/roles/ruby/tasks/main.yml b/provisioning/roles/ruby/tasks/main.yml
index c9c6b64c6..a3b4ec598 100644
--- a/provisioning/roles/ruby/tasks/main.yml
+++ b/provisioning/roles/ruby/tasks/main.yml
@@ -13,7 +13,7 @@
 
 # TODO: Is it possible to extract this list of dependencies automatically from rvm?
 # Or allow rvm to do the install - but that would require the deploy user to have the permissions
-- name: "Ensure ruby-2.4.10 dependencies installed"
+- name: "Ensure ruby-2.5.9 dependencies installed"
   apt: pkg={{ item }}
   with_items:
     - patch
@@ -37,11 +37,11 @@
     - libssl-dev
     - libgmp-dev
 
-- name: Install ruby-2.4.10 with rvm
-  command: /bin/sh -l -c 'rvm install ruby-2.4.10 --autolibs=read-fail' creates=/home/deploy/.rvm/rubies/ruby-2.4.10
+- name: Install ruby-2.5.9 with rvm
+  command: /bin/sh -l -c 'rvm install ruby-2.5.9 --autolibs=read-fail' creates=/home/deploy/.rvm/rubies/ruby-2.5.9
   become_user: deploy
-  notify: Make ruby-2.4.10 the default
+  notify: Make ruby-2.5.9 the default
 
-- name: Install bundler for ruby 2.4.10
-  command: bash -lc "rvm ruby-2.4.10; gem install bundler --version 2.0.2"
+- name: Install bundler for ruby 2.5.9
+  command: bash -lc "rvm ruby-2.5.9; gem install bundler --version 2.0.2"
   become_user: deploy