diff --git a/docker-compose.yml b/docker-compose.yml
index 9541eb4..aa7badf 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -52,6 +52,7 @@ services:
           - INSTALL_XDEBUG=${WORKSPACE_INSTALL_XDEBUG}
           - INSTALL_PHPDBG=${WORKSPACE_INSTALL_PHPDBG}
           - INSTALL_BLACKFIRE=${INSTALL_BLACKFIRE}
+          - INSTALL_GMP=${WORKSPACE_INSTALL_GMP}
           - INSTALL_SOAP=${WORKSPACE_INSTALL_SOAP}
           - INSTALL_LDAP=${WORKSPACE_INSTALL_LDAP}
           - INSTALL_IMAP=${WORKSPACE_INSTALL_IMAP}
diff --git a/env-example b/env-example
index 0b72782..6378c0b 100644
--- a/env-example
+++ b/env-example
@@ -89,6 +89,7 @@ WORKSPACE_INSTALL_SUBVERSION=false
 WORKSPACE_INSTALL_XDEBUG=false
 WORKSPACE_INSTALL_PHPDBG=false
 WORKSPACE_INSTALL_LDAP=false
+WORKSPACE_INSTALL_GMP=false
 WORKSPACE_INSTALL_SOAP=false
 WORKSPACE_INSTALL_IMAP=false
 WORKSPACE_INSTALL_MONGO=false
diff --git a/workspace/Dockerfile b/workspace/Dockerfile
index 2a639f1..0030d95 100644
--- a/workspace/Dockerfile
+++ b/workspace/Dockerfile
@@ -180,6 +180,20 @@ RUN if [ ${INSTALL_DRUSH} = true ]; then \
 
 USER root
 
+ARG INSTALL_GMP=false
+ARG PHP_VERSION=${PHP_VERSION}
+
+RUN if [ ${INSTALL_GMP} = true ]; then \
+  # Install the PHP SOAP extension
+  apt-get -y install php${PHP_VERSION}-gmp \
+;fi
+
+###########################################################################
+# SOAP:
+###########################################################################
+
+USER root
+
 ARG INSTALL_SOAP=false
 
 RUN if [ ${INSTALL_SOAP} = true ]; then \