diff --git a/nselib/vnc.lua b/nselib/vnc.lua
index 8b7cbc4d9..3f706173c 100644
--- a/nselib/vnc.lua
+++ b/nselib/vnc.lua
@@ -552,7 +552,7 @@ VNC = {
       return false, "ERROR: VNC:handshake failed to receive security data"
     end
     for i=1, vncsec.count do
-      table.insert( vncsec.types, string.unpack("B", tmp, i) )
+      table.insert( vncsec.types, (string.unpack("B", tmp, i)) )
     end
     self.vncsec = vncsec
     return true