diff --git a/packages/schema/src/language-server/validator/attribute-application-validator.ts b/packages/schema/src/language-server/validator/attribute-application-validator.ts
index 0de3a5854..9ec2074be 100644
--- a/packages/schema/src/language-server/validator/attribute-application-validator.ts
+++ b/packages/schema/src/language-server/validator/attribute-application-validator.ts
@@ -15,7 +15,13 @@ import {
     isEnum,
     isReferenceExpr,
 } from '@zenstackhq/language/ast';
-import { isDataModelFieldReference, isFutureExpr, isRelationshipField, resolved } from '@zenstackhq/sdk';
+import {
+    isDataModelFieldReference,
+    isDelegateModel,
+    isFutureExpr,
+    isRelationshipField,
+    resolved,
+} from '@zenstackhq/sdk';
 import { ValidationAcceptor, streamAst } from 'langium';
 import pluralize from 'pluralize';
 import { AstValidator } from '../types';
@@ -164,6 +170,31 @@ export default class AttributeApplicationValidator implements AstValidator<Attri
         }
     }
 
+    @check('@@unique')
+    private _checkUnique(attr: AttributeApplication, accept: ValidationAcceptor) {
+        const fields = attr.args[0]?.value;
+        if (fields && isArrayExpr(fields)) {
+            fields.items.forEach((item) => {
+                if (!isReferenceExpr(item)) {
+                    accept('error', `Expecting a field reference`, { node: item });
+                    return;
+                }
+                if (!isDataModelField(item.target.ref)) {
+                    accept('error', `Expecting a field reference`, { node: item });
+                    return;
+                }
+
+                if (item.target.ref.$container !== attr.$container && isDelegateModel(item.target.ref.$container)) {
+                    accept('error', `Cannot use fields inherited from a polymorphic base model in \`@@unique\``, {
+                        node: item,
+                    });
+                }
+            });
+        } else {
+            accept('error', `Expected an array of field references`, { node: fields });
+        }
+    }
+
     private validatePolicyKinds(
         kind: string,
         candidates: string[],
diff --git a/tests/regression/tests/issue-1758.test.ts b/tests/regression/tests/issue-1758.test.ts
new file mode 100644
index 000000000..f07428e8e
--- /dev/null
+++ b/tests/regression/tests/issue-1758.test.ts
@@ -0,0 +1,29 @@
+import { loadModelWithError } from '@zenstackhq/testtools';
+
+describe('issue 1758', () => {
+    it('regression', async () => {
+        await expect(
+            loadModelWithError(
+                `
+            model Organization {
+                id       String @id @default(cuid())
+                contents Content[] @relation("OrganizationContents")
+            }
+
+            model Content {
+                id             String @id @default(cuid())
+                contentType    String
+                organization   Organization @relation("OrganizationContents", fields: [organizationId], references: [id])
+                organizationId String
+                @@delegate(contentType)
+            }
+
+            model Store extends Content {
+                name      String
+                @@unique([organizationId, name])
+            }
+            `
+            )
+        ).resolves.toContain('Cannot use fields inherited from a polymorphic base model in `@@unique`');
+    });
+});