diff --git a/userspace/digwatch/lua/test.lua b/userspace/digwatch/lua/test.lua
index 2e67ddea..e6c0dc47 100644
--- a/userspace/digwatch/lua/test.lua
+++ b/userspace/digwatch/lua/test.lua
@@ -20,7 +20,9 @@ for str in string.gmatch(arg[1], "([^;]+)") do
    doit(str)
 end
 
-compiler.parser.print_ast(state.ast)
+if not (state.ast == nil) then -- can be nil if only macros
+   compiler.parser.print_ast(state.ast)
+end
 
 os.exit(0)