diff --git a/Dockerfile b/Dockerfile
index 469c70cf..bcf61946 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -181,7 +181,7 @@ COPY target/postfix/main.cf target/postfix/master.cf /etc/postfix/
 COPY target/postfix/header_checks.pcre target/postfix/sender_header_filter.pcre target/postfix/sender_login_maps.pcre /etc/postfix/maps/
 RUN echo "" > /etc/aliases && \
   openssl dhparam -out /etc/postfix/dhparams.pem 2048 && \
-  echo "@weekly FILE=`mktemp` ; openssl dhparam -out $FILE 2048 > /dev/null 2>&1 && mv -f $FILE /etc/postfix/dhparams.pem" > /etc/cron.d/dh2048
+  echo "@weekly FILE=\`mktemp\` ; openssl dhparam -out \$FILE 2048 > /dev/null 2>&1 && mv -f \$FILE /etc/postfix/dhparams.pem" > /etc/cron.d/dh2048
 
 
 # Configuring Logs