diff --git a/src/main.cpp b/src/main.cpp
index 2fb07074..906fef91 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -1409,6 +1409,7 @@ int upx_main(int argc, char *argv[]) {
     static char default_argv0[] = "upx";
 
     upx_compiler_sanity_check();
+    // allow serial re-use of main() as a subroutine
     done_output_name = 0;
     opt->reset();