diff --git a/lang/number.c b/lang/number.c
index e5f5f31..175ee5d 100644
--- a/lang/number.c
+++ b/lang/number.c
@@ -6,7 +6,7 @@
 #include "stdio.h"
 #include <stdlib.h>
 
-struct object_class num_class;
+static struct object_class num_class;
 
 struct number {
 	struct object obj;
@@ -22,7 +22,7 @@
 	return (struct object *)num;
 }
 
-void number_cleanup(struct object *obj) {
+static void number_cleanup(struct object *obj) {
 	abort_if(obj->class_data != &num_class,
 		"number_cleanup obj is not a number");
 	struct number *num = (struct number *)obj;
@@ -36,7 +36,8 @@
 	return num->value;
 }
 
-void number_add(struct object *obj, int arg_count, struct object **args) {
+static void number_add(
+	struct object *obj, int arg_count, struct object **args) {
 	abort_if(arg_count != 1, "number_add called with more than 1 argument");
 	abort_if(!args[0], "number_add arg is NULL");
 	abort_if(obj->class_data != &num_class,
@@ -49,10 +50,10 @@
 	args[0] = number_create(added);
 }
 
-struct object_call calls[] = {
+static struct object_call calls[] = {
 	{.name = "Add", .handler = number_add}, {.name = NULL, /* end */}};
 
-struct object_class num_class = {
+static struct object_class num_class = {
 	.cleanup = number_cleanup,
 	.calls = &calls[0],
 };