diff --git a/ets2panda/linter/src/lib/TypeScriptLinter.ts b/ets2panda/linter/src/lib/TypeScriptLinter.ts
index 15cb57df9756729c54421c58b47a3e02152778ff..2bcd9f5d04d06187d10f0e3ed2aa57a268f203fb 100644
--- a/ets2panda/linter/src/lib/TypeScriptLinter.ts
+++ b/ets2panda/linter/src/lib/TypeScriptLinter.ts
@@ -1934,7 +1934,7 @@ export class TypeScriptLinter extends BaseTypeScriptLinter {
       return;
     }
 
-    const extendedIdent = parent.heritageClauses.at(0);
+    const extendedIdent = parent.heritageClauses[0];
 
     if (!TsUtils.hasModifier(propDecl.modifiers, ts.SyntaxKind.ReadonlyKeyword)) {
       return;
@@ -1960,7 +1960,7 @@ export class TypeScriptLinter extends BaseTypeScriptLinter {
       return undefined;
     }
 
-    const extendedType = extended.types.at(0);
+    const extendedType = extended.types[0];
     if (!extendedType) {
       return undefined;
     }