diff --git a/sound-control.sh b/sound-control.sh
index 76bfa51..af7545f 100755
--- a/sound-control.sh
+++ b/sound-control.sh
@@ -38,12 +38,12 @@ function notify_vol {
                 -u normal \
                 -a "Volume" \
                 -h int:value:"${vol}" \
-                "${icon}"
+                "${icon} ${vol}%"
 }
 
 function check_number {
-    if ! [[ -z "${1}" ]] && ! [[ "${1}" =~ '^-?[0-9]+%?$' ]]; then
-        echo "error: not a valid number: \"${1}\""
+    if ! [[ -z "${1}" ]] && ! [[ "${1}" =~ '^[0-9]+%?$' ]]; then
+        echo "error: not a valid value: \"${1}\""
         exit 1
     fi
 }