diff --git a/octave-iso2mesh.spec b/octave-iso2mesh.spec
index e144894..b72ebe7 100644
--- a/octave-iso2mesh.spec
+++ b/octave-iso2mesh.spec
@@ -284,6 +284,8 @@ mv img2mesh.fig inst/
 %build
 %set_build_flags
 cd tools
+# can't use %make_build below because parallel make with CGAL exhausts 
+# vm's memory and crash the building process, use sequential make instead
 make
 cd ../bin
 ln -s tetgen1.5 tetgen