diff --git a/.github/workflows/phpunit.yml b/.github/workflows/phpunit.yml
index 013d7d89..b05c2abf 100644
--- a/.github/workflows/phpunit.yml
+++ b/.github/workflows/phpunit.yml
@@ -13,8 +13,8 @@ jobs:
       uses: shivammathur/setup-php@v2
       with:
         php-version: "8.3"
-        # php extensions also listed in tools/docker-dev/web/Dockerfile
-        extensions: curl,mysql,ldap,pdo,redis
+        # php extensions also listed in tools/docker-dev/web/Dockerfile and README.md
+        extensions: curl,mysql,ldap,pdo,redis,intl
         tools: composer:v2
     - name: Install dependencies
       run: composer install --prefer-dist --no-progress
diff --git a/README.md b/README.md
index 78bcae88..31075a01 100644
--- a/README.md
+++ b/README.md
@@ -21,12 +21,15 @@ Unity Web Portal is a PHP application built in top of MariaDB and LDAP which act
     1. Some HTTP Authentication mechanism (such as Shibboleth SP)
     1. Composer (`apt install composer` on Ubuntu)
     1. PHP Extensions
+        1. `php-cli`
+        1. `php-curl`
+        1. `php-intl`
         1. `php-ldap`
-        2. `php-curl`
-        3. `php-redis`
-        4. `php-cli`
-        5. `php-mysql`
-        6. `php-pdo`
+        1. `php-mbstring`
+        1. `php-mysql`
+        1. `php-pdo`
+        1. `php-redis`
+        1. `php-xml`
 2. Composer packages
     1. `cd` to this repository
     1. Setup git submodules `git submodule update --init --checkout`
diff --git a/tools/docker-dev/web/Dockerfile b/tools/docker-dev/web/Dockerfile
index dc95aa98..40198b24 100644
--- a/tools/docker-dev/web/Dockerfile
+++ b/tools/docker-dev/web/Dockerfile
@@ -2,7 +2,7 @@ FROM ubuntu:24.04
 
 # Web Server Setup
 ARG DEBIAN_FRONTEND=noninteractive
-# php extensions also listed in .github/workflows/phpunit.yml
+# php extensions also listed in .github/workflows/phpunit.yml and README.md
 RUN apt-get update && apt-get install -y \
     apache2 \
     apache2-utils \
@@ -14,7 +14,8 @@ RUN apt-get update && apt-get install -y \
     php-redis \
     php-cli \
     php-mbstring \
-    php-xml
+    php-xml \
+    php-intl
 COPY htpasswd /etc/apache2/.htpasswd
 RUN chown www-data /etc/apache2/.htpasswd
 COPY unity-apache.conf /etc/apache2/sites-available/unity.conf