diff --git a/GNUmakefile b/GNUmakefile
index 3973fdf..ae20472 100644
--- a/GNUmakefile
+++ b/GNUmakefile
@@ -319,8 +319,8 @@ endif
 %.o: %.c $(HDRS) GNUmakefile
 	$(CC) -c $(CPPFLAGS) $(CFLAGS) -o $@ $<
 
-test: TCPPFLAGS+=-D"TEST_ZEROUSR=\"$(shell id -u -n 0)\""
-test: TCPPFLAGS+=-D"TEST_ZEROGRP=\"$(shell id -g -n 0)\""
+test: TCPPFLAGS+=-D"TEST_ZEROUSR=\"$(shell id -u -n 0||echo 0)\""
+test: TCPPFLAGS+=-D"TEST_ZEROGRP=\"$(shell id -g -n 0||echo 0)\""
 test: $(TARGET).test
 	$(RM) extra/pki/session.pem
 	$(MAKE) -C extra/pki testreqs session