diff --git a/index.js b/index.js
index 386c8550..3e793628 100644
--- a/index.js
+++ b/index.js
@@ -131,7 +131,7 @@ module.exports = class Autobase extends ReadyResource {
     this.system = null
     this.version = -1
 
-    this.maxCacheSize = handlers.maxCacheSize || null
+    this.maxCacheSize = handlers.maxCacheSize || 0 // 0 means the hyperbee default cache size will be used
 
     const {
       ackInterval = DEFAULT_ACK_INTERVAL,
diff --git a/test/basic.js b/test/basic.js
index 646f5bce..aa2771a1 100644
--- a/test/basic.js
+++ b/test/basic.js
@@ -1589,11 +1589,11 @@ test('basic - maxCacheSize opt', async t => {
   t.is(base.system.db.maxCacheSize, 10, 'maxCacheSize applied to sys db')
 })
 
-test('basic - maxCacheSize has null default', async t => {
+test('basic - maxCacheSize has 0 default', async t => {
   const [store] = await createStores(1, t)
   const base = new Autobase(store.namespace('with-cache'))
   await base.ready()
-  t.is(base.maxCacheSize, null, 'maxCacheSize default null')
+  t.is(base.maxCacheSize, 0, 'maxCacheSize default 0')
 })
 
 // todo: this test is hard, probably have to rely on ff to recover