diff --git a/src/type/repository-build-definition.js b/src/type/repository-build-definition.js
index e32c900b..d0293307 100644
--- a/src/type/repository-build-definition.js
+++ b/src/type/repository-build-definition.js
@@ -9,6 +9,12 @@ const metapackageDefinition = require('./metapackage-definition');
  * Defines release build instructions for a git repository.
  */
 class repositoryBuildDefinition {
+  /**
+   * @type String|null Identifier of this repository in the build config, used to
+   *  target it individually from a release refs file
+   */
+  key = null;
+
   /**
    * @type String|null Git Repository URL
    */
@@ -79,9 +85,10 @@ class repositoryBuildDefinition {
   extraRefToRelease = [];
 
   /**
-   * @param {{repoUrl: String, packageDirs: Array, packageIndividual: Array, packageMetaFromDirs: Array, vendor: String, ref: String, fromTag: String, skipTags: {Object}, transform: Object.<String,Array>, fixVersions: {Object}, packageReplacements: {Object}, extraRefToRelease: Array, extraMetapackages: Array}}
+   * @param {{key: String, repoUrl: String, packageDirs: Array, packageIndividual: Array, packageMetaFromDirs: Array, vendor: String, ref: String, fromTag: String, skipTags: {Object}, transform: Object.<String,Array>, fixVersions: {Object}, packageReplacements: {Object}, extraRefToRelease: Array, extraMetapackages: Array}}
    */
   constructor(options) {
+    this.key = options.key || this.key;
     this.repoUrl = options.repoUrl || this.repoUrl;
 
     this.vendor = options.vendor || this.vendor;
diff --git a/tests/unit/type/repository-build-definition.test.js b/tests/unit/type/repository-build-definition.test.js
index 838c8cd7..af9f2ab8 100644
--- a/tests/unit/type/repository-build-definition.test.js
+++ b/tests/unit/type/repository-build-definition.test.js
@@ -24,6 +24,11 @@ describe('repositoryBuildDefinition', () => {
         expect(def.ref).toBeNull();
       });
 
+      it('should use null for key when not provided', () => {
+        const def = new repositoryBuildDefinition({});
+        expect(def.key).toBeNull();
+      });
+
       it('should use null for fromTag when not provided', () => {
         const def = new repositoryBuildDefinition({});
         expect(def.fromTag).toBeNull();
@@ -63,6 +68,11 @@ describe('repositoryBuildDefinition', () => {
         expect(def.ref).toBe('2.4-develop');
       });
 
+      it('should use provided key', () => {
+        const def = new repositoryBuildDefinition({ key: 'magento2' });
+        expect(def.key).toBe('magento2');
+      });
+
       it('should use provided fromTag', () => {
         const def = new repositoryBuildDefinition({ fromTag: '2.4.0' });
         expect(def.fromTag).toBe('2.4.0');
diff --git a/tests/unit/utils.test.js b/tests/unit/utils.test.js
index b71eaebf..7c0ab85e 100644
--- a/tests/unit/utils.test.js
+++ b/tests/unit/utils.test.js
@@ -496,8 +496,8 @@ describe('mergeBuildConfigs', () => {
       const b = { 'my-repo': { repoUrl: 'https://example.com' } };
       const result = mergeBuildConfigs(a, b);
 
-      // The key is added to the repositoryBuildDefinition - verify via the object
       expect(result).toHaveLength(1);
+      expect(result[0].key).toBe('my-repo');
     });
 
     it('should override values from a with values from b', () => {