diff --git a/asyncforge.js b/asyncforge.js
index 2ac45a4..b3d3f87 100644
--- a/asyncforge.js
+++ b/asyncforge.js
@@ -36,7 +36,10 @@ function memo (name) {
 
   function get () {
     const store = asyncLocalStorage.getStore()
-    return store?.[sym]
+    if (!store) {
+      throw new Error(`asyncforge store is not initialized for ${name}`)
+    }
+    return store[sym]
   }
 
   function set (value) {
diff --git a/test/do-not-start-memo.test.js b/test/do-not-start-memo.test.js
index 13e6c52..267e517 100644
--- a/test/do-not-start-memo.test.js
+++ b/test/do-not-start-memo.test.js
@@ -8,7 +8,7 @@ test('memo without start', async (t) => {
   const p = tspl(t, { plan: 6 })
   const a = memo()
 
-  p.deepStrictEqual(a(), undefined)
+  p.throws(() => a(), { message: 'asyncforge store is not initialized for memo0' })
   a.set({ value: 'bar' })
   p.deepStrictEqual(a(), { value: 'bar' })
 
@@ -38,11 +38,20 @@ test('memo without start', async (t) => {
   await p.completed
 })
 
+test('memo with name', async (t) => {
+  const p = tspl(t, { plan: 1 })
+  const a = memo('custom-name')
+
+  p.throws(() => a(), { message: 'asyncforge store is not initialized for custom-name' })
+
+  await p.completed
+})
+
 test('nested', async (t) => {
   const p = tspl(t, { plan: 5 })
   const a = memo()
 
-  p.deepStrictEqual(a(), undefined)
+  p.throws(() => a(), { message: 'asyncforge store is not initialized for memo1' })
   a.set({ value: 'bar' })
   p.deepStrictEqual(a(), { value: 'bar' })