diff --git a/packages/sdk/src/utils.ts b/packages/sdk/src/utils.ts
index d32962f11..a32abc068 100644
--- a/packages/sdk/src/utils.ts
+++ b/packages/sdk/src/utils.ts
@@ -218,11 +218,14 @@ export function isIdField(field: DataModelField) {
         return true;
     }
 
+    // NOTE: we have to use name to match fields because the fields
+    // may be inherited from an abstract base and have cloned identities
+
     const model = field.$container as DataModel;
 
     // model-level @@id attribute with a list of fields
     const modelLevelIds = getModelIdFields(model);
-    if (modelLevelIds.includes(field)) {
+    if (modelLevelIds.map((f) => f.name).includes(field.name)) {
         return true;
     }
 
@@ -234,12 +237,12 @@ export function isIdField(field: DataModelField) {
     // then, the first field with @unique can be used as id
     const firstUniqueField = model.fields.find((f) => hasAttribute(f, '@unique'));
     if (firstUniqueField) {
-        return firstUniqueField === field;
+        return firstUniqueField.name === field.name;
     }
 
     // last, the first model level @@unique can be used as id
     const modelLevelUnique = getModelUniqueFields(model);
-    if (modelLevelUnique.includes(field)) {
+    if (modelLevelUnique.map((f) => f.name).includes(field.name)) {
         return true;
     }
 
diff --git a/tests/integration/tests/regression/issue-1129.test.ts b/tests/integration/tests/regression/issue-1129.test.ts
new file mode 100644
index 000000000..49198a5cb
--- /dev/null
+++ b/tests/integration/tests/regression/issue-1129.test.ts
@@ -0,0 +1,87 @@
+import { createPostgresDb, dropPostgresDb, loadSchema } from '@zenstackhq/testtools';
+
+describe('Regression for issue 1129', () => {
+    it('regression', async () => {
+        let prisma;
+        const dbUrl = await createPostgresDb('regression-issue-1129');
+
+        try {
+            const r = await loadSchema(
+                `
+            model Relation1 {
+              id String @id @default(cuid())
+              field1 String
+              concrete Concrete[]
+              @@allow('all', true)
+            }
+            
+            model Relation2 {
+              id String @id @default(cuid())
+              field2 String
+              concrete Concrete[]
+              @@allow('all', true)
+            }
+            
+            abstract model WithRelation1 {
+              relation1Id String
+              relation1 Relation1 @relation(fields: [relation1Id], references: [id])
+            }
+            abstract model WithRelation2 {
+              relation2Id String
+              relation2 Relation2 @relation(fields: [relation2Id], references: [id])
+            }
+            
+            model Concrete extends WithRelation1, WithRelation2 {
+              concreteField String
+              @@id([relation1Id, relation2Id])
+              @@allow('all', true)
+            }
+            `,
+                { provider: 'postgresql', dbUrl }
+            );
+
+            prisma = r.prisma;
+            const db = r.enhance();
+
+            await db.$transaction(async (tx: any) => {
+                await tx.relation2.createMany({
+                    data: [
+                        {
+                            id: 'relation2Id1',
+                            field2: 'field2Value1',
+                        },
+                        {
+                            id: 'relation2Id2',
+                            field2: 'field2Value2',
+                        },
+                    ],
+                });
+
+                await tx.relation1.create({
+                    data: {
+                        field1: 'field1Value',
+                        concrete: {
+                            createMany: {
+                                data: [
+                                    {
+                                        concreteField: 'concreteFieldValue1',
+                                        relation2Id: 'relation2Id1',
+                                    },
+                                    {
+                                        concreteField: 'concreteFieldValue2',
+                                        relation2Id: 'relation2Id2',
+                                    },
+                                ],
+                            },
+                        },
+                    },
+                });
+            });
+        } finally {
+            if (prisma) {
+                await prisma.$disconnect();
+            }
+            await dropPostgresDb('regression-issue-1129');
+        }
+    });
+});