diff --git a/build/start-container.sh b/build/start-container.sh
index 3877c2c..a1aecc9 100644
--- a/build/start-container.sh
+++ b/build/start-container.sh
@@ -1,7 +1,7 @@
 #! /usr/bin/env sh
 
 if [ -n "${SMTP_HOST_FILE}" ]; then
-    SMTP_HOST=$cat ${SMTP_HOST_FILE});
+    SMTP_HOST=$(cat ${SMTP_HOST_FILE});
 fi
 
 if [ -n "${SMTP_PORT_FILE}" ]; then