diff --git a/README.md b/README.md
index 4035027..25493d0 100644
--- a/README.md
+++ b/README.md
@@ -6,7 +6,8 @@ This action slug and expose some github variables.
 
 - put the variable content in lower case,
 - replace any caracter by `-` except `0-9` and `a-z`,
-- limit the string size to 63 caracters
+- remove leading and trailing `-` caracter,
+- limit the string size to 63 caracters.
 
 ## Environement Variables
 
diff --git a/entrypoint.sh b/entrypoint.sh
index fa3e84c..2d0d8ac 100755
--- a/entrypoint.sh
+++ b/entrypoint.sh
@@ -3,6 +3,7 @@
 slug_ref() {
     echo "$1" \
          | tr "[:upper:]" "[:lower:]" \
+         | sed -r 's#refs/.*/##;s/[~\^]+//g;s/[^a-zA-Z0-9]+/-/g;s/^-+\|-+$//g;s/^-*//;s/-*$//' \
          | cut -c1-63
 }