diff --git a/overlay/mruby-builder/mruby/stub.c b/overlay/mruby-builder/mruby/stub.c
index 8c25d860..f733cd13 100644
--- a/overlay/mruby-builder/mruby/stub.c
+++ b/overlay/mruby-builder/mruby/stub.c
@@ -1,17 +1,44 @@
-#include <mruby.h>
-#include <mruby/irep.h>
-#include "irep.c"
 #include <stdlib.h>
+#include <string.h>
+
+#include <mruby.h>
+#include <mruby/array.h>
+#include <mruby/irep.h>
+#include <mruby/variable.h>
+
+// Assumes this is produced by builder.nix
+#include "irep.c"
 
 int
-main(void)
+main(int argc, char **argv)
 {
+	int i;
+	mrb_value ARGV;
+	mrb_sym dollar_zero;
+	mrb_sym program_name;
 	mrb_state *mrb = mrb_open();
+
 	if (!mrb) {
 		/* handle error */
 		printf("[FATAL] Could not open mruby.\n");
 		exit(1);
 	}
+
+	ARGV = mrb_ary_new_capa(mrb, argc);
+	// Skip the program name here.
+	for (i = 1; i < argc; i++) {
+		mrb_ary_push(mrb, ARGV, mrb_str_new(mrb, argv[i], strlen(argv[i])));
+	}
+	mrb_define_global_const(mrb, "ARGV", ARGV);
+
+	// $0
+	dollar_zero = mrb_intern_lit(mrb, "$0");
+	mrb_gv_set(mrb, dollar_zero, mrb_str_new(mrb, argv[0], strlen(argv[0])));
+
+	// $PROGRAM_NAME
+	program_name = mrb_intern_lit(mrb, "$PROGRAM_NAME");
+	mrb_gv_set(mrb, program_name, mrb_str_new(mrb, argv[0], strlen(argv[0])));
+
 	mrb_load_irep(mrb, ruby_irep);
 
 	if (mrb->exc) {