diff --git a/Dockerfile b/Dockerfile
index 3848b74..ec735ba 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -42,6 +42,7 @@ RUN apk add --no-cache \
     php7-xmlwriter \
     php7-tokenizer \
     php7-curl \
+    php7-simplexml \
     composer
 
 WORKDIR /var/lib/roundcube