--- configure.ac.orig	2016-12-16 08:05:02 UTC
+++ configure.ac
@@ -35,6 +35,7 @@ AC_PROG_CXX
 AM_INIT_AUTOMAKE([1.11.1 color-tests silent-rules tar-pax no-texinfo.tex -Wall -Wno-portability])
 AM_SILENT_RULES([yes])
 AC_PROG_CXX
+AC_PROG_GREP
 AC_PROG_INSTALL
 AC_PROG_RANLIB
 AC_PROG_LN_S
