diff --git a/functions/common.sh b/functions/common.sh
index 9d0d956..29b3285 100644
--- a/functions/common.sh
+++ b/functions/common.sh
@@ -3,7 +3,7 @@
 cleanup_and_exit()
 {
     trap EXIT
-    exit ${1:-0}
+    exit "${1:-0}"
 }
 
 fail_exit()
@@ -20,19 +20,20 @@
     eval "exec $fd>>$LOCKFILE"
     case $1 in
         "set")
-            flock -x -n $fd \
+            flock -x -n "$fd" \
                 || fail_exit "Process already running. Lockfile: $LOCKFILE"
             ;;
         "unset")
-            flock -u $fd
-            rm -f $LOCKFILE
+            flock -u "$fd"
+            [ -f "$LOCKFILE" ] && rm -f "$LOCKFILE"
             ;;
         "wait")
             local TIMEOUT=${2:-3600}
-            [ "${VERBOSE}" == "true" ] \
-                && echo "Waiting of concurrent process (lockfile: $LOCKFILE, timeout = $TIMEOUT seconds) ..."
-            flock -x -w $TIMEOUT $fd \
+            [ "$IS_VERBOSE" == "true" ] \
+                && echo "[INFO] Waiting of concurrent process (lockfile: $LOCKFILE, timeout = $TIMEOUT seconds) ..."
+            flock -x -w "$TIMEOUT" "$fd" \
                 || fail_exit "Timeout error (lockfile: $LOCKFILE)"
+            [ "${IS_VERBOSE}" == "true" ] && echo "[INFO] Done"
             ;;
     esac
 }