diff --git a/nselib/giop.lua b/nselib/giop.lua
index 09d349b24..8ed6363c5 100644
--- a/nselib/giop.lua
+++ b/nselib/giop.lua
@@ -235,6 +235,10 @@ Packet.GIOP.reply = {
       pos, tmp = bin.unpack( bo .. "I", self.GIOP.data, pos )
     elseif ( self.GIOP.version == Constants.VERSION_1_0 ) then
       pos, tmp = bin.unpack( bo .. "I", self.GIOP.data )
+    else
+      local err = ("Unknown GIOP version: %s"):format(self.GIOP.version)
+      stdnse.debug2("recv: %s", err)
+      return false, err
     end
 
     for i=1, tmp do