diff --git a/src/freedombone-sipfreeext b/src/freedombone-sipfreeext
index 5fbb07b2..f1f181e5 100755
--- a/src/freedombone-sipfreeext
+++ b/src/freedombone-sipfreeext
@@ -35,35 +35,23 @@ extensions=()
 
 # get the used extensions
 IFS=''
-while read line; do
-    if [[ "$line" == *"<extension>"* ]]; then
-        ext=$(echo "$line" | awk -F '>' '{print $2}' | awk -F '<' '{print $1}')
-        extensions+=($ext)
-    fi
-    if [[ "$line" == *'</provision>' ]]; then
-        break
-    fi
-done < $CONFIG_FILE
+for line in $(cat $CONFIG_FILE | grep "extension"); do
+    extnum=$(echo "$line" | awk -F '>' '{print $2}' | awk -F '<' '{print $1}')
+    extensions+=($extnum)
+done
 
-#echo "used extensions:"
-#echo $extensions
-#echo " "
-
-# which is the first available unused extension ?
-for ext in $(seq 201 299);
-do
-    is_used=
-    for i in "${extensions[@]}"
-    do
-        if [[ "$i" == "$ext" ]]; then
-            is_used=1
-            break
-        fi
-    done
-    if [ ! $is_used ]; then
-        echo $ext;
+# find the max extension number
+maxnum=201
+for i in ${extensions[@]}; do
+    if [ $i -gt $maxnum ]; then
+        maxnum=$i
         break
     fi
 done
 
+if [ $maxnum -gt 299 ]; then
+	exit 1
+fi
+
+echo $(($maxnum + 1))
 exit 0