diff --git a/src/arch/posix/Makefile.inc b/src/arch/posix/Makefile.inc
index 66655b5046ac51904740eccfa1b0344ce5ee04cc..17cdfd9a23026bcb07ef243aaf39bb938df2842f 100644
--- a/src/arch/posix/Makefile.inc
+++ b/src/arch/posix/Makefile.inc
@@ -47,7 +47,7 @@ arch_clean:
 
 arch_help:
 	@echo "posix specific flags:"
-	@echo "    - none -"
+	@echo "    gpio_trace = 0 (show GPIO changes on stdout)"
 
 arch_info:
 	@echo "Counter Overflow: 18446744073709551616/1"