diff --git a/CHANGELOG.md b/CHANGELOG.md
index 27a2e5287..f0cbea108 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,14 @@
 
 All changes that impact users of this module are documented in this file, in the [Common Changelog](https://common-changelog.org) format with some additional specifications defined in the CONTRIBUTING file. This codebase adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## Unreleased [patch]
+
+> Development of this release was supported by [Reset Tech](https://www.reset.tech).
+
+### Fixed
+
+- Fix declaration validation when a new service is added along with a filters file
+
 ## 10.6.0 - 2026-01-26
 
 > Development of this release was supported by [Reset Tech](https://www.reset.tech).
diff --git a/scripts/declarations/utils/index.js b/scripts/declarations/utils/index.js
index 6b3338a9c..ce9385aa5 100644
--- a/scripts/declarations/utils/index.js
+++ b/scripts/declarations/utils/index.js
@@ -50,6 +50,10 @@ export default class DeclarationUtils {
       if (modifiedFilePath.endsWith('.filters.js') || modifiedFilePath.endsWith('.filters.history.js')) {
         const declaration = await this.getJSONFromFile(this.defaultBranch, `declarations/${serviceId}.json`);
 
+        if (!declaration) { // Happens when the file declaration exists in the branch but not in the default branch
+          return;
+        }
+
         servicesTermsTypes[serviceId] = Object.keys(declaration.terms); // Considering how rarely filters are used, simply return all term types that could potentially be impacted to spare implementing a function change check
 
         return;
diff --git a/scripts/declarations/utils/index.test.js b/scripts/declarations/utils/index.test.js
index c60babae0..2b26033b6 100644
--- a/scripts/declarations/utils/index.test.js
+++ b/scripts/declarations/utils/index.test.js
@@ -188,6 +188,23 @@ describe('DeclarationUtils', () => {
       });
     });
 
+    context('when a new declaration has been added along with a filters file', () => {
+      before(async () => {
+        await fs.writeFile(path.resolve(SUBJECT_PATH, COMMIT_PATHS.serviceB), JSON.stringify(FIXTURES.serviceB.content, null, 2));
+        await fs.writeFile(path.resolve(SUBJECT_PATH, './declarations/ServiceB.filters.js'), 'module.exports = {};');
+        await declarationUtils.git.add([ COMMIT_PATHS.serviceB, './declarations/ServiceB.filters.js' ]);
+        await declarationUtils.git.commit('Add declaration with filters for new service');
+      });
+      after(removeLatestCommit);
+
+      it('returns the added service ID along with all its terms types', async () => {
+        expect(await declarationUtils.getModifiedServicesAndTermsTypes()).to.deep.equal({
+          services: ['ServiceB'],
+          servicesTermsTypes: { ServiceB: ['Terms of Service'] },
+        });
+      });
+    });
+
     context('when history file is modified without declaration changes', () => {
       before(() => commitChanges(COMMIT_PATHS.serviceAHistory, FIXTURES.serviceATermsUpdatedHistory.content));
       after(removeLatestCommit);