diff --git a/packages/@sanity/form-builder/src/sanity/inputs/client-adapters/reference.js b/packages/@sanity/form-builder/src/sanity/inputs/client-adapters/reference.js
index 2a5abe93827..c7af46f0c08 100644
--- a/packages/@sanity/form-builder/src/sanity/inputs/client-adapters/reference.js
+++ b/packages/@sanity/form-builder/src/sanity/inputs/client-adapters/reference.js
@@ -34,7 +34,7 @@ export function search(textTerm, referenceType) {
   const terms = textTerm.split(/\s+/)
   const typeConstraints = referenceType.to.map(type => buildConstraintFromType(type, terms))
 
-  const query = `*[!(_id in path('drafts.**')) && ${typeConstraints.map(wrapInParens).join('||')}]`
+  const query = `*[!(_id in path('drafts.**')) && (${typeConstraints.map(wrapInParens).join('||')})]`
 
   return client.observable.fetch(query, {term: `${textTerm}*`})
 }
diff --git a/packages/test-studio/schemas/references.js b/packages/test-studio/schemas/references.js
index f03753e9803..5d89541ae5b 100644
--- a/packages/test-studio/schemas/references.js
+++ b/packages/test-studio/schemas/references.js
@@ -20,6 +20,12 @@ export default {
       weak: true,
       to: {type: 'author'}
     },
+    {
+      title: 'Reference to book or author',
+      name: 'multiTypeRef',
+      type: 'reference',
+      to: [{type: 'book'}, {type: 'author'}]
+    },
     {
       name: 'array',
       type: 'array',