diff --git a/src/doesQueryContain.js b/src/doesQueryContain.js
index 72844d9..d96e56d 100644
--- a/src/doesQueryContain.js
+++ b/src/doesQueryContain.js
@@ -24,14 +24,16 @@ export default function doesQueryContain(
   ids?: ?Set<any>,
   idField?: string = 'id'
 ): boolean {
-  const potentialAncestors = getPotentialAncestors(types[typename])
+  const targetType = types[typename]
+  if (!targetType) throw new Error(`type not found: ${typename}`)
+  const potentialAncestors = getPotentialAncestors(targetType)
 
   function doesNodeContain(
     node: Node,
     data: any,
     type: Type,
   ): boolean {
-    if (type.name === typename) {
+    if (type === targetType) {
       if (!ids) return true
       return data && ids.has(data[idField])
     }
diff --git a/test/doesQueryContain.js b/test/doesQueryContain.js
index b429ca2..c8b6019 100644
--- a/test/doesQueryContain.js
+++ b/test/doesQueryContain.js
@@ -8,6 +8,20 @@ import gql from 'graphql-tag'
 import doesQueryContain from '../src/doesQueryContain'
 
 describe(`doesQueryContain`, function () {
+  it(`throws if type is not found`, function () {
+    const document = gql`{
+      Device(id: 1) {
+        id
+      }
+    }`
+    let error
+    try {
+      doesQueryContain(document, types, 'Deviceg')
+    } catch (err) {
+      error = err
+    }
+    expect(error).to.exist
+  })
   it(`basic test`, function () {
     const document = gql`{
       Device(id: 1) {