diff --git a/subr/build_init.subr b/subr/build_init.subr
index 3164398..db5b822 100644
--- a/subr/build_init.subr
+++ b/subr/build_init.subr
@@ -11,6 +11,9 @@ build_fini() {
 build_init() {
 	local __="" _env_vars="" _env_vars_except="" _env_var="" _log_last_fname="" _log_last_ts="" _vname="" _vname_val="";
 	set -o noglob; umask 022;
+	if ! awk -V | grep -q "^GNU Awk "; then
+		ex_rtl_log_msg failexit "Error: awk(1) in \$PATH must be GNU Awk.";
+	fi;
 	if [ -z "${DEFAULT_BUILD_CPUS}" ]\
 	&& [ -e /proc/cpuinfo ]; then
 		DEFAULT_BUILD_CPUS=$(awk '/^processor/{cpus++} END{print cpus}' /proc/cpuinfo);