diff --git a/BioArchLinux/r-openmx/PKGBUILD b/BioArchLinux/r-openmx/PKGBUILD
index 65c28dbe36..7c7930728a 100644
--- a/BioArchLinux/r-openmx/PKGBUILD
+++ b/BioArchLinux/r-openmx/PKGBUILD
@@ -46,6 +46,8 @@ source=("https://cran.r-project.org/src/contrib/${_pkgname}_${_pkgver}.tar.gz")
 sha256sums=('65c50ce09f9c006b41b7311ec05eba3ae77926d84fb44e3905905208404826ed')
 
 build() {
+  # restrict the usage of cpu. Usage of RAM is OK.
+  export MAKE="make -j5" 
   R CMD INSTALL ${_pkgname}_${_pkgver}.tar.gz -l "${srcdir}"
 }