diff --git a/ssh_filter_btrbk.sh b/ssh_filter_btrbk.sh
index 18c1b3fb..c1616e5a 100755
--- a/ssh_filter_btrbk.sh
+++ b/ssh_filter_btrbk.sh
@@ -1,9 +1,13 @@
 #!/bin/sh
 
-set -e -u
 
+# initialise and sanitise the shell execution environment
+unset -v IFS
+export LC_ALL=C
 export PATH='/usr/bin:/bin'
 
+set -e -u
+
 enable_log=
 restrict_path_list=
 allow_list=