diff --git a/build.sh b/build.sh
index 2a6d25b..9a3b57b 100755
--- a/build.sh
+++ b/build.sh
@@ -30,7 +30,7 @@ buildp_dispatch() {
 					ex_rtl_log_msg failexit "Error: package \`${_pkg_restart}' unknown.";
 				fi;
 			done;
-			if ! ex_pkg_dispatch "invariants" "ALL" "ALL" buildp_dispatch; then
+			if ! ex_pkg_dispatch "invariants" "ALL" "ALL" buildp_dispatch ""; then
 				break;
 			fi;
 			buildp_dispatch finish_build; ;;
diff --git a/subr/ex_pkg_dispatch.subr b/subr/ex_pkg_dispatch.subr
index 45653b4..9a06fd3 100644
--- a/subr/ex_pkg_dispatch.subr
+++ b/subr/ex_pkg_dispatch.subr
@@ -101,7 +101,9 @@ ex_pkg_dispatch() {
 		fi;
 	done;
 	"${_dispatch_fn}" finish_target "" "${_tgt_name}";
-	ex_rtl_set_var_unsafe "${_pkgs_found_vname}" "${_pkgs_found}";
+	if [ -n "${_pkgs_found_vname}" ]; then
+		ex_rtl_set_var_unsafe "${_pkgs_found_vname}" "${_pkgs_found}";
+	fi;
 };
 
 # vim:filetype=sh