diff --git a/lang/number.c b/lang/number.c
index fc01c3d..6d96478 100644
--- a/lang/number.c
+++ b/lang/number.c
@@ -22,6 +22,7 @@
 }
 
 static void number_cleanup(Object obj) {
+	abort_if(obj == NULL, "number_cleanup obj is NULL");
 	abort_if(obj->class_data != &num_class,
 		"number_cleanup obj is not a number");
 	struct number *num = (struct number *)obj;
@@ -39,32 +40,20 @@
 	int arg_count = vm_stack_depth(state);
 	abort_if(arg_count != 2, "number_add called without 2 arguments");
 	Object arg1 = vm_stack_get(state, 1);
-	abort_if(!arg1, "number_add arg is NULL");
-	abort_if(arg1->class_data != &num_class,
-		"number_add arg is not a number");
-	struct number *numA = (struct number *)obj;
-	struct number *numB = (struct number *)arg1;
-	int added = numA->value + numB->value;
+	int added = number_value(obj) + number_value(arg1);
 	vm_stack_set(state, 0, number_create(added));
 	vm_stack_drop(state, 1);
 	object_drop(&arg1);
-	numB = NULL;
 }
 
 static void number_minus(VmState state, Object obj) {
 	int arg_count = vm_stack_depth(state);
 	abort_if(arg_count != 2, "number_minus called without 2 arguments");
 	Object arg1 = vm_stack_get(state, 1);
-	abort_if(!arg1, "number_minus arg is NULL");
-	abort_if(arg1->class_data != &num_class,
-		"number_minus arg is not a number");
-	struct number *numA = (struct number *)obj;
-	struct number *numB = (struct number *)arg1;
-	int subbed = numA->value - numB->value;
+	int subbed = number_value(obj) - number_value(arg1);
 	vm_stack_set(state, 0, number_create(subbed));
 	vm_stack_drop(state, 1);
 	object_drop(&arg1);
-	numB = NULL;
 }
 
 static struct object_call calls[] = {{.name = "Add", .handler = number_add},