diff --git a/packages/runtime/src/enhancements/policy/policy-utils.ts b/packages/runtime/src/enhancements/policy/policy-utils.ts
index 12c8c57be..98c49957c 100644
--- a/packages/runtime/src/enhancements/policy/policy-utils.ts
+++ b/packages/runtime/src/enhancements/policy/policy-utils.ts
@@ -515,7 +515,7 @@ export class PolicyUtil {
                     throw this.unknownError(`missing backLink field ${currField.backLink} in ${currField.type}`);
                 }
 
-                if (backLinkField.isArray) {
+                if (backLinkField.isArray && !mutating) {
                     // many-side of relationship, wrap with "some" query
                     currQuery[currField.backLink] = { some: { ...visitWhere } };
                 } else {
diff --git a/tests/integration/tests/cli/plugins.test.ts b/tests/integration/tests/cli/plugins.test.ts
index d2461c4ec..005a0f69b 100644
--- a/tests/integration/tests/cli/plugins.test.ts
+++ b/tests/integration/tests/cli/plugins.test.ts
@@ -71,7 +71,7 @@ describe('CLI Plugins Tests', () => {
             'zod@3.21.1',
             'react',
             'swr',
-            '@tanstack/react-query',
+            '@tanstack/react-query@^4.0.0',
             '@trpc/server',
             '@prisma/client@^4.0.0',
             `${path.join(__dirname, '../../../../.build/zenstackhq-language-' + ver + '.tgz')}`,
diff --git a/tests/integration/tests/enhancements/with-policy/nested-to-many.test.ts b/tests/integration/tests/enhancements/with-policy/nested-to-many.test.ts
index fa7059faa..b112aeeb1 100644
--- a/tests/integration/tests/enhancements/with-policy/nested-to-many.test.ts
+++ b/tests/integration/tests/enhancements/with-policy/nested-to-many.test.ts
@@ -284,7 +284,7 @@ describe('With Policy:nested to-many', () => {
         expect(r.m2).toEqual(expect.arrayContaining([expect.objectContaining({ id: '2', value: 3 })]));
     });
 
-    it('update with create', async () => {
+    it('update with create from one to many', async () => {
         const { withPolicy } = await loadSchema(
             `
         model M1 {
@@ -341,6 +341,56 @@ describe('With Policy:nested to-many', () => {
         expect(r.m2).toHaveLength(3);
     });
 
+    it('update with create from many to one', async () => {
+        const { withPolicy } = await loadSchema(
+            `
+        model M1 {
+            id String @id @default(uuid())
+            value Int
+            m2 M2[]
+        
+            @@allow('read', true)
+            @@allow('create', value > 0)
+            @@allow('update', value > 1)
+        }
+        
+        model M2 {
+            id String @id @default(uuid())
+            m1 M1? @relation(fields: [m1Id], references:[id])
+            m1Id String?
+        
+            @@allow('all', true)
+        }
+        `
+        );
+
+        const db = withPolicy();
+
+        await db.m2.create({ data: { id: '1' } });
+
+        await expect(
+            db.m2.update({
+                where: { id: '1' },
+                data: {
+                    m1: {
+                        create: { value: 0 },
+                    },
+                },
+            })
+        ).toBeRejectedByPolicy();
+
+        await expect(
+            db.m2.update({
+                where: { id: '1' },
+                data: {
+                    m1: {
+                        create: { value: 1 },
+                    },
+                },
+            })
+        ).toResolveTruthy();
+    });
+
     it('update with delete', async () => {
         const { withPolicy, prisma } = await loadSchema(
             `
diff --git a/tests/integration/tests/regression/issue-764.test.ts b/tests/integration/tests/regression/issue-764.test.ts
new file mode 100644
index 000000000..8e64a15d8
--- /dev/null
+++ b/tests/integration/tests/regression/issue-764.test.ts
@@ -0,0 +1,49 @@
+import { loadSchema } from '@zenstackhq/testtools';
+
+describe('Regression: issue 764', () => {
+    it('regression', async () => {
+        const { prisma, enhance } = await loadSchema(
+            `
+        model User {
+            id    Int     @id @default(autoincrement())
+            name  String
+            
+            post   Post? @relation(fields: [postId], references: [id])
+            postId Int?
+            
+            @@allow('all', true)
+        }
+            
+        model Post {
+            id    Int    @id @default(autoincrement())
+            title String
+            User  User[]
+            
+            @@allow('all', true)
+        }
+        `
+        );
+
+        const db = enhance();
+
+        const user = await prisma.user.create({
+            data: { name: 'Me' },
+        });
+
+        await db.user.update({
+            where: { id: user.id },
+            data: {
+                post: {
+                    upsert: {
+                        create: {
+                            title: 'Hello World',
+                        },
+                        update: {
+                            title: 'Hello World',
+                        },
+                    },
+                },
+            },
+        });
+    });
+});