diff --git a/functions.sh b/functions.sh
index 2c4b32b..51ae802 100755
--- a/functions.sh
+++ b/functions.sh
@@ -30,7 +30,10 @@ function _pkcs11module() {
     [ -n "${P11M:+x}" ] && PKCS11_MODULE=${P11M}
     [ -n "${P11M:+x}" ] && tmux set-environment P11M ${P11M}
 
-    tmux set-environment PKCS11_MODULE ${PKCS11_MODULE}
+    if [ -n "${TMUX}" ]; then
+        tmux set-environment PKCS11_MODULE ${PKCS11_MODULE}
+        tmux set-environment -g PKCS11_MODULE ${PKCS11_MODULE}
+    fi
 
 }
 ## this function updates in combination with PROMPT_COMMAND the shell-environment-variables in tmux-sessions,