diff --git a/lang/number.c b/lang/number.c
index ef76256..e6b7a0b 100644
--- a/lang/number.c
+++ b/lang/number.c
@@ -37,8 +37,7 @@
 
 static void number_add(
 	struct object *obj, int arg_count, struct object **args) {
-	abort_if(
-		arg_count != 2, "number_add called with more than 2 arguments");
+	abort_if(arg_count != 2, "number_add called without 2 arguments");
 	abort_if(args[0] != NULL, "number_add return is not NULL");
 	abort_if(!args[1], "number_add arg is NULL");
 	abort_if(obj->class_data != &num_class,
@@ -51,8 +50,23 @@
 	args[0] = number_create(added);
 }
 
-static struct object_call calls[] = {
-	{.name = "Add", .handler = number_add}, {.name = NULL, /* end */}};
+static void number_minus(
+	struct object *obj, int arg_count, struct object **args) {
+	abort_if(arg_count != 2, "number_minus called without 2 arguments");
+	abort_if(args[0] != NULL, "number_minus return is not NULL");
+	abort_if(!args[1], "number_minus arg is NULL");
+	abort_if(obj->class_data != &num_class,
+		"number_minus obj is not a number");
+	abort_if(args[1]->class_data != &num_class,
+		"number_minus arg is not a number");
+	struct number *numA = (struct number *)obj;
+	struct number *numB = (struct number *)args[1];
+	int subbed = numA->value - numB->value;
+	args[0] = number_create(subbed);
+}
+
+static struct object_call calls[] = {{.name = "Add", .handler = number_add},
+	{.name = "Minus", .handler = number_minus}, {.name = NULL, /* end */}};
 
 static struct object_class num_class = {
 	.cleanup = number_cleanup,