diff --git a/lang/func.c b/lang/func.c
index 464accf..785d834 100644
--- a/lang/func.c
+++ b/lang/func.c
@@ -4,23 +4,17 @@
 #include "bytecode.h"
 #include "error.h"
 #include "object.h"
-#include <stdlib.h>
+#include <stddef.h>
 
 static struct object_class func_class;
 
-struct func {
-	struct object obj;
-};
-
 Object func_create(void) {
-	struct func *func = malloc(sizeof(struct func));
-	abort_if(!func, "unable to allocate func");
-	func->obj.class_data = &func_class;
-	func->obj.ref_count = 1;
-	return (Object)func;
+	Object obj = object_create(&func_class, 1);
+	abort_if(!obj, "unable to allocate func");
+	return obj;
 }
 
-static void func_cleanup(Object obj) { free(obj); }
+static void func_cleanup(Object obj) { (void)obj; }
 
 static void func_call(VmState state, Object obj) {
 	(void)obj;
diff --git a/lang/number.c b/lang/number.c
index f904f66..72fa887 100644
--- a/lang/number.c
+++ b/lang/number.c
@@ -3,30 +3,26 @@
 
 #include "error.h"
 #include "object.h"
-#include <stdlib.h>
+#include <stddef.h>
 
 static struct object_class num_class;
 
 struct number {
-	struct object obj;
 	int value;
 };
 
 Object number_create(int value) {
-	struct number *num = malloc(sizeof(struct number));
-	abort_if(!num, "unable to allocate number");
-	num->obj.class_data = &num_class;
-	num->obj.ref_count = 1;
+	Object obj = object_create(&num_class, sizeof(struct number));
+	abort_if(!obj, "unable to allocate number");
+	struct number *num = (struct number *)object_priv(obj, &num_class);
 	num->value = value;
-	return (Object)num;
+	return obj;
 }
 
-static void number_cleanup(Object obj) { free(obj); }
+static void number_cleanup(Object obj) { (void)obj; }
 
 int number_value(Object obj) {
-	abort_if(obj->class_data != &num_class,
-		"number_value obj is not a number");
-	struct number *num = (struct number *)obj;
+	struct number *num = (struct number *)object_priv(obj, &num_class);
 	return num->value;
 }
 
diff --git a/lang/object.c b/lang/object.c
index 76ec3b9..027f1ad 100644
--- a/lang/object.c
+++ b/lang/object.c
@@ -3,9 +3,35 @@
 
 #include "object.h"
 #include "error.h"
+#include <stdatomic.h>
 #include <stddef.h>
+#include <stdlib.h>
 #include <string.h>
 
+struct object {
+	struct object_class *class_data;
+	atomic_int ref_count;
+	char priv_data[];
+};
+
+Object object_create(struct object_class *class, int priv_size) {
+	abort_if(priv_size < 1, "object_create: priv_size too small");
+	size_t size = sizeof(struct object) + priv_size;
+	struct object *obj = calloc(size, 1);
+	abort_if(
+		obj == NULL, "object_create: not enough memory for an objects");
+	obj->class_data = class;
+	obj->ref_count = 1;
+	return (Object)obj;
+}
+
+char *object_priv(Object object, struct object_class *class) {
+	abort_if(object == NULL, "object_priv: no object");
+	struct object *obj = (struct object *)object;
+	abort_if(obj->class_data != class, "object_priv: incompatible class");
+	return object->priv_data;
+}
+
 void object_hold(Object obj) {
 	abort_if(obj == NULL, "object_hold holding NULL");
 	atomic_fetch_add_explicit(&obj->ref_count, 1, memory_order_relaxed);
@@ -19,6 +45,7 @@
 	if (count == 1) {
 		// We were the last user of the object, clean it up
 		obj->class_data->cleanup(obj);
+		free(obj);
 	}
 	*objptr = NULL;
 }
diff --git a/lang/object.h b/lang/object.h
index 05264db..2714f59 100644
--- a/lang/object.h
+++ b/lang/object.h
@@ -5,7 +5,6 @@
 #define OBJECT_H
 
 #include "vm.h"
-#include <stdatomic.h>
 
 // Dispatchable object call
 struct object_call {
@@ -20,13 +19,8 @@
 		*calls; // Points to array terminated by call with NULL name
 };
 
-// Object structure used by all classes
-// Place this at the start of your private structure and cast accordingly
-// Make sure to compile with -fno-strict-aliasing
-struct object {
-	struct object_class *class_data;
-	atomic_int ref_count;
-};
+Object object_create(struct object_class *class, int priv_size);
+char *object_priv(Object object, struct object_class *class);
 
 // Adds a reference to an object
 void object_hold(Object obj);