diff --git a/check_mdb b/check_mdb
index 69ec22e..dafd5fc 100755
--- a/check_mdb
+++ b/check_mdb
@@ -90,7 +90,7 @@ do
 	esac
 done
 
-CMD="$MDB_STAT -e $DB_PATH"
+CMD="$MDB_STAT -ef $DB_PATH"
 debug "mdb_stat command = '$CMD'"
 
 if [ -n "$SUDO_USER" ]
@@ -111,8 +111,12 @@ then
 	exit 3
 fi
 
+raw_used_pages=$( echo -e "$OUTPUT"|grep -E '^ +Number of pages used: '|sed 's/^ \+Number of pages used: \([0-9]\+\)$/\1/' )
+free_pages=$( echo -e "$OUTPUT"|grep -E '^ +Free pages: '|sed 's/^ \+Free pages: \([0-9]\+\)$/\1/' )
+let used_pages=raw_used_pages-free_pages
+debug "Used/free pages: $raw_used_pages / $free_pages. Real used pages: $used_pages"
+
 max_pages=$( echo -e "$OUTPUT"|grep -E '^ +Max pages: '|sed 's/^ \+Max pages: \([0-9]\+\)$/\1/' )
-used_pages=$( echo -e "$OUTPUT"|grep -E '^ +Number of pages used: '|sed 's/^ \+Number of pages used: \([0-9]\+\)$/\1/' )
 let perc_used=$used_pages*100/$max_pages
 debug "Used/max pages: $used_pages / $max_pages ($perc_used%)"