diff --git a/packages/@aws-cdk/aws-iam/lib/principals.ts b/packages/@aws-cdk/aws-iam/lib/principals.ts
index 3a411287d6114..9475707b1ad82 100644
--- a/packages/@aws-cdk/aws-iam/lib/principals.ts
+++ b/packages/@aws-cdk/aws-iam/lib/principals.ts
@@ -459,7 +459,7 @@ export class AccountPrincipal extends ArnPrincipal {
 
   /**
    *
-   * @param accountId AWS account ID (i.e. 123456789012)
+   * @param accountId AWS account ID (i.e. '123456789012')
    */
   constructor(public readonly accountId: any) {
     super(new StackDependentToken(stack => `arn:${stack.partition}:iam::${accountId}:root`).toString());
@@ -936,4 +936,4 @@ export function validateConditionObject(x: unknown): asserts x is Record<string,
   if (!x || typeof x !== 'object' || Array.isArray(x)) {
     throw new Error('A Condition should be represented as a map of operator to value');
   }
-}
\ No newline at end of file
+}