# CHAP installation error **URL:** \ **Category:** User discussions\ **Created:** [April 23, 2024, 6:20am UTC](https://gromacs.bioexcel.eu/t/chap-installation-error/8956 "2024-04-23T06:20:06Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![veerubiotech](https://avatars.discourse-cdn.com/v4/letter/v/e480ec/32.png) [@veerubiotech](https://gromacs.bioexcel.eu/u/veerubiotech)\ **Post date:** [April 23, 2024, 6:20am UTC](https://gromacs.bioexcel.eu/t/chap-installation-error/8956/1 "2024-04-23T06:20:06Z")
GROMACS version: 2024.1 GROMACS modification: Yes/No Here post your question I am compiling the CHAP program on WSL2 (Ubuntu). It requires gromcs to be installed. I have gromacs installed and available in the terminal. However, when executing make command, I encountered the following error- In file included from /mnt/d/Simulation/chap-version\_0\_9\_1/src/aggregation/boltzmann\_energy\_calculator.cpp:25: /mnt/d/Simulation/chap-version\_0\_9\_1/include/aggregation/boltzmann\_energy\_calculator.hpp:30:10: fatal error: gromacs/utility/real.h: No such file or directory 30 | #include “gromacs/utility/real.h” | ^ ~~~~~~~~~~~~~~~~~~~~~~~ compilation terminated. make[2]: \*\*\* [CMakeFiles/chap.dir/build.make:76: CMakeFiles/chap.dir/src/aggregation/boltzmann\_energy\_calculator.cpp.o] Error 1 make[1]: \*\*\* [CMakeFiles/Makefile2:157: CMakeFiles/chap.dir/all] Error 2 make: \*\*\* [Makefile:146: all] Error 2 I can not find the real.h file. how can specify this file to make command. Thank you ---
**Author:** ![al42and](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/al42and/32/1393_2.png) [@al42and](https://gromacs.bioexcel.eu/u/al42and)\ **Post date:** [April 23, 2024, 11:33am UTC](https://gromacs.bioexcel.eu/t/chap-installation-error/8956/2 "2024-04-23T11:33:49Z")
Hi! This missing header problem can be solved by adding `-DGMX_INSTALL_LEGACY_API=ON` to GROMACS’s `cmake` call and then reinstalling GROMACS. However, it looks like CHAP only supports GROMACS up to 2018: [Issue with "Make" command · Issue #34 · channotation/chap · GitHub](https://github.com/channotation/chap/issues/34#issuecomment-869122300), so just installing the missing `real.h` header is apparently not enough.