diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6a17df9..a09c05b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
+### Added
+- Include `pickleId` in `AssembledTestCase` ([#26](https://github.com/cucumber/javascript-core/pull/26))
 
 ## [0.5.1] - 2025-09-17
 
diff --git a/cucumber-core.api.md b/cucumber-core.api.md
index a433a84..8b96c5f 100644
--- a/cucumber-core.api.md
+++ b/cucumber-core.api.md
@@ -30,6 +30,7 @@ export class AmbiguousError extends Error {
 export interface AssembledTestCase {
     id: string;
     name: string;
+    pickleId: string;
     sourceReference: SourceReference;
     testSteps: ReadonlyArray<AssembledTestStep>;
     toMessage(): TestCase;
diff --git a/src/makeTestPlan.ts b/src/makeTestPlan.ts
index 8846d29..5089405 100644
--- a/src/makeTestPlan.ts
+++ b/src/makeTestPlan.ts
@@ -52,6 +52,7 @@ export function makeTestPlan(
       const location = query.findLocationOf(pickle) as MessagesLocation
       return {
         id: newId(),
+        pickleId: pickle.id,
         name: strategy.reduce(lineage, pickle),
         sourceReference: {
           uri: pickle.uri,
@@ -65,7 +66,7 @@ export function makeTestPlan(
         toMessage() {
           return {
             id: this.id,
-            pickleId: pickle.id,
+            pickleId: this.pickleId,
             testSteps: this.testSteps.map((step) => step.toMessage()),
             testRunStartedId,
           }
diff --git a/src/types.ts b/src/types.ts
index 52c4a81..1cd60b1 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -471,6 +471,10 @@ export interface AssembledTestCase {
    * A unique identifier for this test case
    */
   id: string
+  /**
+   * The id of the pickle from which this test case is derived
+   */
+  pickleId: string
   /**
    * A non-unique name for this test case
    * @remarks