diff --git a/upgrade.sh b/upgrade.sh
index 2501333..fc8f1b6 100755
--- a/upgrade.sh
+++ b/upgrade.sh
@@ -1,6 +1,8 @@
 #!/usr/bin/env bash
 # Upgrade script
 
+set -x
+
 if [ $# -eq 0 ]
   then
       echo 'Pass new LimeSurvey Version tag:'
@@ -20,7 +22,8 @@ fi
 
 # Download, unzip and chmod LimeSurvey from official GitHub repository
 wget -P /tmp "https://github.com/LimeSurvey/LimeSurvey/archive/${NEW_VERSION}.tar.gz"
-SHA256_CHECKSUM=$(sha256 "${NEW_VERSION}.tar.gz")
+
+SHA256_CHECKSUM=$(sha256sum "/tmp/${NEW_VERSION}.tar.gz" | awk '{ print $1 }')
 
 # Update lines in the files
 sed -r -i -e "s/[0-9]+(\.[0-9]+)+\+[0-9]+/$NEW_VERSION/" apache/Dockerfile fpm/Dockerfile fpm-alpine/Dockerfile