diff --git a/packages/schema/src/plugins/zod/transformer.ts b/packages/schema/src/plugins/zod/transformer.ts
index f79c945cc..16e1451bf 100644
--- a/packages/schema/src/plugins/zod/transformer.ts
+++ b/packages/schema/src/plugins/zod/transformer.ts
@@ -342,7 +342,21 @@ export default class Transformer {
             // "Input" or "NestedInput" suffix
             mappedInputTypeName += match[4];
 
-            processedInputType = { ...inputType, type: mappedInputTypeName };
+            // Prisma's naming is inconsistent for update input types, so we need
+            // to check for a few other candidates and use the one that matches
+            // a DMMF input type name
+            const candidates = [mappedInputTypeName];
+            if (mappedInputTypeName.includes('UpdateOne')) {
+                candidates.push(...candidates.map((name) => name.replace('UpdateOne', 'Update')));
+            }
+            if (mappedInputTypeName.includes('NestedInput')) {
+                candidates.push(...candidates.map((name) => name.replace('NestedInput', 'Input')));
+            }
+
+            const finalMappedName =
+                candidates.find((name) => this.inputObjectTypes.some((it) => it.name === name)) ?? mappedInputTypeName;
+
+            processedInputType = { ...inputType, type: finalMappedName };
         }
         return processedInputType;
     }
diff --git a/packages/sdk/src/utils.ts b/packages/sdk/src/utils.ts
index 09a538f77..0427ab4f0 100644
--- a/packages/sdk/src/utils.ts
+++ b/packages/sdk/src/utils.ts
@@ -659,8 +659,16 @@ export function getRelationBackLink(field: DataModelField) {
 
     const targetModel = field.type.reference.ref as DataModel;
 
+    const sameField = (f1: DataModelField, f2: DataModelField) => {
+        // for fields inherited from a delegate model, always use
+        // the base to compare
+        const parent1 = f1.$inheritedFrom ?? f1.$container;
+        const parent2 = f2.$inheritedFrom ?? f2.$container;
+        return f1.name === f2.name && parent1 === parent2;
+    };
+
     for (const otherField of targetModel.fields) {
-        if (otherField === field) {
+        if (sameField(otherField, field)) {
             // backlink field is never self
             continue;
         }
diff --git a/tests/regression/tests/issue-2226.test.ts b/tests/regression/tests/issue-2226.test.ts
new file mode 100644
index 000000000..8dc55bfad
--- /dev/null
+++ b/tests/regression/tests/issue-2226.test.ts
@@ -0,0 +1,31 @@
+import { loadSchema } from '@zenstackhq/testtools';
+
+describe('issue 2226', () => {
+    it('regression', async () => {
+        const { zodSchemas } = await loadSchema(
+            `
+model Registration {
+    id String @id
+    regType String
+    @@delegate(regType)
+
+    replacedRegistrationId String?
+    replacedRegistration   Registration?  @relation("ReplacedBy", fields: [replacedRegistrationId], references: [id])
+    replacements           Registration[] @relation("ReplacedBy")
+}
+
+// Delegated subtype
+model RegistrationFramework extends Registration {
+}
+`,
+            { fullZod: true }
+        );
+
+        const schema = zodSchemas.objects.RegistrationFrameworkUpdateInputObjectSchema;
+        expect(schema).toBeDefined();
+        const parsed = schema.safeParse({
+            replacedRegistrationId: '123',
+        });
+        expect(parsed.success).toBe(true);
+    });
+});