diff --git a/acme.sh b/acme.sh
index aa8a43e..2308e3f 100755
--- a/acme.sh
+++ b/acme.sh
@@ -3104,7 +3104,7 @@ _process() {
         HTTPS_INSECURE="1"
         ;;
     --ca-bundle)
-        _ca_bundle=$(readlink -f $2)
+        _ca_bundle="$(readlink -f $2)"
         CA_BUNDLE="$_ca_bundle"
         shift
         ;;