[BUG] Katalon Studio 8.0.0 java.lang.ClassFormatError

Updated Katalon studio version from 7.4.0 to 8.0. I download the Katalon 8.0 from the github instead of updating directly from Katalon - Help - Check for Updates. Every time I run a script, I am getting this error: java.lang.ClassFormatError: Illegal method name “dataBasePackage.Sql.connectDB” in class CustomKeywords

I tried to delete Libs & bin folder from project location and open Katalon studio 8.0 again but it didn’t help. I am not able to trouble shoot the issue. Can any one help me here. Thanks in advance.

Hi @sshah,

This issue is a known issue from v7.9.0 when we upgrading Eclipse framework (including Groovy-Eclipse plugin), we planned to fix it in v8.0.5. For now, you can keep using KS from v7.4.0 to v7.8.2.


Hi @sshah @duyluong @Shin I am having same challenge in katalon studio V8.2.0


try removing <projectdir>/.cache folder.

In this folder stored the compiled class files of your custom keywords. The error indicates that a class file in the folder is in bad format: perhaps the file is there but has 0-bytes. I don’t know why.

By removing the .cache folder, you can let Katalon Studio to build the keyword class cleanly.