diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8f741e9..eadf74a 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]
+### Changed
+- Allow ExpressionsGroup.children to be optional ([#43](https://github.com/cucumber/javascript-core/pull/43))
 
 ## [0.8.2] - 2026-01-12
 ### Changed
diff --git a/package-lock.json b/package-lock.json
index ef1dd8b..faf7240 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -9,7 +9,7 @@
       "version": "0.8.2",
       "license": "MIT",
       "devDependencies": {
-        "@cucumber/cucumber-expressions": "^18.0.1",
+        "@cucumber/cucumber-expressions": "^19.0.0",
         "@cucumber/gherkin": "^38.0.0",
         "@cucumber/messages": "^32.0.0",
         "@cucumber/query": "^15.0.0",
@@ -66,9 +66,9 @@
       }
     },
     "node_modules/@cucumber/cucumber-expressions": {
-      "version": "18.0.1",
-      "resolved": "https://registry.npmjs.org/@cucumber/cucumber-expressions/-/cucumber-expressions-18.0.1.tgz",
-      "integrity": "sha512-NSid6bI+7UlgMywl5octojY5NXnxR9uq+JisjOrO52VbFsQM6gTWuQFE8syI10KnIBEdPzuEUSVEeZ0VFzRnZA==",
+      "version": "19.0.0",
+      "resolved": "https://registry.npmjs.org/@cucumber/cucumber-expressions/-/cucumber-expressions-19.0.0.tgz",
+      "integrity": "sha512-4FKoOQh2Uf6F6/Ln+1OxuK8LkTg6PyAqekhf2Ix8zqV2M54sH+m7XNJNLhOFOAW/t9nxzRbw2CcvXbCLjcvHZg==",
       "dev": true,
       "license": "MIT",
       "dependencies": {
@@ -91,7 +91,6 @@
       "integrity": "sha512-1OSoW+GQvFUNAl6tdP2CTBexTXMNJF0094goVUcvugtQeXtJ0K8sCP0xbq7GGoiezs/eJAAOD03+zAPT64orHQ==",
       "dev": true,
       "license": "MIT",
-      "peer": true,
       "dependencies": {
         "class-transformer": "0.5.1",
         "reflect-metadata": "0.2.2"
@@ -684,7 +683,6 @@
       "integrity": "sha512-PRA911Blj99jR5RMeTunVbNXMF6Lp4vZXnk5GQjcnUWUTsrXtekg/pnmFFI2u/I36Y/2bITGS30GZCXei6uNkA==",
       "dev": true,
       "license": "MIT",
-      "peer": true,
       "dependencies": {
         "fast-deep-equal": "^3.1.3",
         "json-schema-traverse": "^1.0.0",
@@ -1090,7 +1088,6 @@
       "integrity": "sha512-kVIaQE9vrN9RLCQMQ3iyRlVJpTiDUY6woHGb30JDkfJErqrQEmtdWH3gV0PBAfGZgQXoqzXOO0T3K6ioApbbAA==",
       "dev": true,
       "license": "MIT",
-      "peer": true,
       "dependencies": {
         "@typescript-eslint/scope-manager": "8.37.0",
         "@typescript-eslint/types": "8.37.0",
@@ -1283,7 +1280,6 @@
       "integrity": "sha512-NZyJarBfL7nWwIq+FDL6Zp/yHEhePMNnnJ0y3qfieCrmNvYct8uvtiV41UvlSe6apAfk0fY1FbWx+NwfmpvtTg==",
       "dev": true,
       "license": "MIT",
-      "peer": true,
       "bin": {
         "acorn": "bin/acorn"
       },
@@ -1526,7 +1522,6 @@
       "integrity": "sha512-NUPRluOfOiTKBKvWPtSD4PhFvWCqOi0BGStNWs57X9js7XGTprSmFoz5F0tWhR4WPjNeR9jXqdC7/UpSJTnlRg==",
       "dev": true,
       "license": "MIT",
-      "peer": true,
       "engines": {
         "node": ">=18"
       }
@@ -1822,7 +1817,6 @@
       "integrity": "sha512-QldCVh/ztyKJJZLr4jXNUByx3gR+TDYZCRXEktiZoUR3PGy4qCmSbkxcIle8GEwGpb5JBZazlaJ/CxLidXdEbQ==",
       "dev": true,
       "license": "MIT",
-      "peer": true,
       "dependencies": {
         "@eslint-community/eslint-utils": "^4.2.0",
         "@eslint-community/regexpp": "^4.12.1",
@@ -3610,7 +3604,6 @@
       "integrity": "sha512-p1diW6TqL9L07nNxvRMM7hMMw4c5XOo/1ibL4aAIGmSAt9slTE1Xgw5KWuof2uTOvCg9BY7ZRi+GaF+7sfgPeQ==",
       "dev": true,
       "license": "Apache-2.0",
-      "peer": true,
       "bin": {
         "tsc": "bin/tsc",
         "tsserver": "bin/tsserver"
@@ -3655,7 +3648,8 @@
       "resolved": "https://registry.npmjs.org/undici-types/-/undici-types-7.8.0.tgz",
       "integrity": "sha512-9UJ2xGDvQ43tYyVMpuHlsgApydB8ZKfVYTsLDhXkFL/6gfkp+U8xTGdh8pMJv1SpZna0zxG1DwsKZsreLbXBxw==",
       "dev": true,
-      "license": "MIT"
+      "license": "MIT",
+      "peer": true
     },
     "node_modules/universalify": {
       "version": "2.0.1",
diff --git a/package.json b/package.json
index 1e226b9..591b3eb 100644
--- a/package.json
+++ b/package.json
@@ -37,7 +37,7 @@
     "@cucumber/tag-expressions": "*"
   },
   "devDependencies": {
-    "@cucumber/cucumber-expressions": "^18.0.1",
+    "@cucumber/cucumber-expressions": "^19.0.0",
     "@cucumber/gherkin": "^38.0.0",
     "@cucumber/messages": "^32.0.0",
     "@cucumber/query": "^15.0.0",
diff --git a/src/makeTestPlan.spec.ts b/src/makeTestPlan.spec.ts
index ca396f7..8ee92db 100644
--- a/src/makeTestPlan.spec.ts
+++ b/src/makeTestPlan.spec.ts
@@ -555,10 +555,21 @@ describe('makeTestPlan', () => {
           fn: sinon.stub(),
           sourceReference: { uri: 'hooks.js', location: { line: 2, column: 1 } },
         })
+        .parameterType({
+          name: 'flight',
+          regexp: /([A-Z]{3})-([A-Z]{3})/,
+          transformer: sinon.stub(),
+          sourceReference: { uri: 'hooks.js', location: { line: 1, column: 1 } },
+        })
         .step({
           pattern: 'we scored {int} out of {int}',
           fn: sinon.stub(),
-          sourceReference: { uri: 'steps.js', location: { line: 1, column: 1 } },
+          sourceReference: { uri: 'steps.js', location: { line: 2, column: 1 } },
+        })
+        .step({
+          pattern: '{flight} has been delayed',
+          fn: sinon.stub(),
+          sourceReference: { uri: 'steps.js', location: { line: 3, column: 1 } },
         })
         .build()
 
@@ -572,23 +583,22 @@ describe('makeTestPlan', () => {
       expect(result.toEnvelopes()).to.deep.eq([
         {
           testCase: {
-            id: '7',
-            pickleId: '3',
+            id: '11',
+            pickleId: '5',
             testSteps: [
               {
-                hookId: '4',
-                id: '8',
+                hookId: '6',
+                id: '12',
               },
               {
-                id: '9',
-                pickleStepId: '2',
-                stepDefinitionIds: ['6'],
+                id: '13',
+                pickleStepId: '3',
+                stepDefinitionIds: ['9'],
                 stepMatchArgumentsLists: [
                   {
                     stepMatchArguments: [
                       {
                         group: {
-                          children: [],
                           start: 10,
                           value: '4',
                         },
@@ -596,7 +606,6 @@ describe('makeTestPlan', () => {
                       },
                       {
                         group: {
-                          children: [],
                           start: 19,
                           value: '5',
                         },
@@ -607,8 +616,36 @@ describe('makeTestPlan', () => {
                 ],
               },
               {
-                hookId: '5',
-                id: '10',
+                id: '14',
+                pickleStepId: '4',
+                stepDefinitionIds: ['10'],
+                stepMatchArgumentsLists: [
+                  {
+                    stepMatchArguments: [
+                      {
+                        group: {
+                          children: [
+                            {
+                              start: 0,
+                              value: 'LHR',
+                            },
+                            {
+                              start: 4,
+                              value: 'CDG',
+                            },
+                          ],
+                          start: 0,
+                          value: 'LHR-CDG',
+                        },
+                        parameterTypeName: 'flight',
+                      },
+                    ],
+                  },
+                ],
+              },
+              {
+                hookId: '7',
+                id: '15',
               },
             ],
             testRunStartedId,
diff --git a/src/makeTestPlan.ts b/src/makeTestPlan.ts
index eede45b..b8d0125 100644
--- a/src/makeTestPlan.ts
+++ b/src/makeTestPlan.ts
@@ -221,6 +221,12 @@ function fromPickleSteps(
 }
 
 function mapArgumentGroup(group: ExpressionsGroup): MessagesGroup {
+  if (!group.children) {
+    return {
+      start: group.start,
+      value: group.value,
+    }
+  }
   return {
     start: group.start,
     value: group.value,
diff --git a/testdata/parameters.feature b/testdata/parameters.feature
index 9289c67..ee3e24d 100644
--- a/testdata/parameters.feature
+++ b/testdata/parameters.feature
@@ -1,3 +1,4 @@
 Feature: a feature
   Scenario: a scenario
-    Given we scored 4 out of 5
\ No newline at end of file
+    Given we scored 4 out of 5
+    And LHR-CDG has been delayed
\ No newline at end of file