diff --git a/Dockerfile b/Dockerfile
index 3b5b585..bedd573 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -57,7 +57,7 @@ RUN ldconfig
 # add user (+ group workaround for ArchLinux)
 RUN useradd -m worker -G cdrom \
     && if [ -n "${optical_gid}" ]; then groupadd -f -g "${optical_gid}" optical \
-    && usermod -a -G optical worker; fi
+    && usermod -a -G optical worker; fi \
     && mkdir -p /output /home/worker/.config/whipper \
     && chown worker: /output /home/worker/.config/whipper
 VOLUME ["/home/worker/.config/whipper", "/output"]