diff --git a/.changeset/nice-cars-cover.md b/.changeset/nice-cars-cover.md
new file mode 100644
index 000000000..8cf1ec724
--- /dev/null
+++ b/.changeset/nice-cars-cover.md
@@ -0,0 +1,5 @@
+---
+"lingo.dev": patch
+---
+
+fix --frozen flag
diff --git a/packages/cli/src/cli/cmd/i18n.ts b/packages/cli/src/cli/cmd/i18n.ts
index 11c133455..3be84a710 100644
--- a/packages/cli/src/cli/cmd/i18n.ts
+++ b/packages/cli/src/cli/cmd/i18n.ts
@@ -151,31 +151,68 @@ export default new Command()
 
       if (flags.frozen) {
         ora.start("Checking for lockfile updates...");
-        let requiresUpdate = false;
-        for (const bucket of buckets) {
+        let requiresUpdate: string | null = null;
+        bucketLoop: for (const bucket of buckets) {
           for (const bucketConfig of bucket.config) {
             const sourceLocale = resolveOverridenLocale(i18nConfig!.locale.source, bucketConfig.delimiter);
 
             const bucketLoader = createBucketLoader(bucket.type, bucketConfig.pathPattern, {
               isCacheRestore: false,
               defaultLocale: sourceLocale,
+              returnUnlocalizedKeys: true,
             });
             bucketLoader.setDefaultLocale(sourceLocale);
             await bucketLoader.init();
 
-            const sourceData = await bucketLoader.pull(i18nConfig!.locale.source);
+            const { unlocalizable: sourceUnlocalizable, ...sourceData } = await bucketLoader.pull(
+              i18nConfig!.locale.source,
+            );
             const updatedSourceData = lockfileHelper.extractUpdatedData(bucketConfig.pathPattern, sourceData);
 
+            // translation was updated in the source file
             if (Object.keys(updatedSourceData).length > 0) {
-              requiresUpdate = true;
-              break;
+              requiresUpdate = "updated";
+              break bucketLoop;
+            }
+
+            for (const _targetLocale of targetLocales) {
+              const targetLocale = resolveOverridenLocale(_targetLocale, bucketConfig.delimiter);
+              const { unlocalizable: targetUnlocalizable, ...targetData } = await bucketLoader.pull(targetLocale);
+
+              const missingKeys = _.difference(Object.keys(sourceData), Object.keys(targetData));
+              const extraKeys = _.difference(Object.keys(targetData), Object.keys(sourceData));
+              const unlocalizableDataDiff = !_.isEqual(sourceUnlocalizable, targetUnlocalizable);
+
+              // translation is missing in the target file
+              if (missingKeys.length > 0) {
+                requiresUpdate = "missing";
+                break bucketLoop;
+              }
+
+              // target file has extra translations
+              if (extraKeys.length > 0) {
+                requiresUpdate = "extra";
+                break bucketLoop;
+              }
+
+              // unlocalizable keys do not match
+              if (unlocalizableDataDiff) {
+                requiresUpdate = "unlocalizable";
+                break bucketLoop;
+              }
             }
           }
-          if (requiresUpdate) break;
         }
 
         if (requiresUpdate) {
-          ora.fail("Localization data has changed; please update i18n.lock or run without --frozen.");
+          const message = {
+            updated: "Source file has been updated.",
+            missing: "Target file is missing translations.",
+            extra: "Target file has extra translations not present in the source file.",
+            unlocalizable: "Unlocalizable data (such as booleans, dates, URLs, etc.) do not match.",
+          }[requiresUpdate];
+          ora.fail(`Localization data has changed; please update i18n.lock or run without --frozen.`);
+          ora.fail(`  Details: ${message}`);
           process.exit(1);
         } else {
           ora.succeed("No lockfile updates required.");
diff --git a/packages/cli/src/cli/loaders/index.ts b/packages/cli/src/cli/loaders/index.ts
index f04b7dfd2..0ac1ad9eb 100644
--- a/packages/cli/src/cli/loaders/index.ts
+++ b/packages/cli/src/cli/loaders/index.ts
@@ -32,6 +32,7 @@ import createVueJsonLoader from "./vue-json";
 
 type BucketLoaderOptions = {
   isCacheRestore: boolean;
+  returnUnlocalizedKeys?: boolean;
   defaultLocale: string;
 };
 
@@ -49,7 +50,7 @@ export default function createBucketLoader(
         createAndroidLoader(),
         createFlatLoader(),
         createSyncLoader(),
-        createUnlocalizableLoader(options.isCacheRestore),
+        createUnlocalizableLoader(options.isCacheRestore, options.returnUnlocalizedKeys),
       );
     case "csv":
       return composeLoaders(
@@ -57,7 +58,7 @@ export default function createBucketLoader(
         createCsvLoader(),
         createFlatLoader(),
         createSyncLoader(),
-        createUnlocalizableLoader(options.isCacheRestore),
+        createUnlocalizableLoader(options.isCacheRestore, options.returnUnlocalizedKeys),
       );
     case "html":
       return composeLoaders(
@@ -65,7 +66,7 @@ export default function createBucketLoader(
         createPrettierLoader({ parser: "html", alwaysFormat: true }),
         createHtmlLoader(),
         createSyncLoader(),
-        createUnlocalizableLoader(options.isCacheRestore),
+        createUnlocalizableLoader(options.isCacheRestore, options.returnUnlocalizedKeys),
       );
     case "json":
       return composeLoaders(
@@ -74,7 +75,7 @@ export default function createBucketLoader(
         createJsonLoader(),
         createFlatLoader(),
         createSyncLoader(),
-        createUnlocalizableLoader(options.isCacheRestore),
+        createUnlocalizableLoader(options.isCacheRestore, options.returnUnlocalizedKeys),
       );
     case "markdown":
       return composeLoaders(
@@ -82,7 +83,7 @@ export default function createBucketLoader(
         createPrettierLoader({ parser: "markdown" }),
         createMarkdownLoader(),
         createSyncLoader(),
-        createUnlocalizableLoader(options.isCacheRestore),
+        createUnlocalizableLoader(options.isCacheRestore, options.returnUnlocalizedKeys),
       );
     case "po":
       return composeLoaders(
@@ -90,7 +91,7 @@ export default function createBucketLoader(
         createPoLoader(),
         createFlatLoader(),
         createSyncLoader(),
-        createUnlocalizableLoader(options.isCacheRestore),
+        createUnlocalizableLoader(options.isCacheRestore, options.returnUnlocalizedKeys),
         createVariableLoader({ type: "python" }),
       );
     case "properties":
@@ -98,14 +99,14 @@ export default function createBucketLoader(
         createTextFileLoader(bucketPathPattern),
         createPropertiesLoader(),
         createSyncLoader(),
-        createUnlocalizableLoader(options.isCacheRestore),
+        createUnlocalizableLoader(options.isCacheRestore, options.returnUnlocalizedKeys),
       );
     case "xcode-strings":
       return composeLoaders(
         createTextFileLoader(bucketPathPattern),
         createXcodeStringsLoader(),
         createSyncLoader(),
-        createUnlocalizableLoader(options.isCacheRestore),
+        createUnlocalizableLoader(options.isCacheRestore, options.returnUnlocalizedKeys),
       );
     case "xcode-stringsdict":
       return composeLoaders(
@@ -113,7 +114,7 @@ export default function createBucketLoader(
         createXcodeStringsdictLoader(),
         createFlatLoader(),
         createSyncLoader(),
-        createUnlocalizableLoader(options.isCacheRestore),
+        createUnlocalizableLoader(options.isCacheRestore, options.returnUnlocalizedKeys),
       );
     case "xcode-xcstrings":
       return composeLoaders(
@@ -123,7 +124,7 @@ export default function createBucketLoader(
         createXcodeXcstringsLoader(options.defaultLocale),
         createFlatLoader(),
         createSyncLoader(),
-        createUnlocalizableLoader(options.isCacheRestore),
+        createUnlocalizableLoader(options.isCacheRestore, options.returnUnlocalizedKeys),
         createVariableLoader({ type: "ieee" }),
       );
     case "yaml":
@@ -133,7 +134,7 @@ export default function createBucketLoader(
         createYamlLoader(),
         createFlatLoader(),
         createSyncLoader(),
-        createUnlocalizableLoader(options.isCacheRestore),
+        createUnlocalizableLoader(options.isCacheRestore, options.returnUnlocalizedKeys),
       );
     case "yaml-root-key":
       return composeLoaders(
@@ -143,7 +144,7 @@ export default function createBucketLoader(
         createRootKeyLoader(true),
         createFlatLoader(),
         createSyncLoader(),
-        createUnlocalizableLoader(options.isCacheRestore),
+        createUnlocalizableLoader(options.isCacheRestore, options.returnUnlocalizedKeys),
       );
     case "flutter":
       return composeLoaders(
@@ -153,7 +154,7 @@ export default function createBucketLoader(
         createFlutterLoader(),
         createFlatLoader(),
         createSyncLoader(),
-        createUnlocalizableLoader(options.isCacheRestore),
+        createUnlocalizableLoader(options.isCacheRestore, options.returnUnlocalizedKeys),
       );
     case "xliff":
       return composeLoaders(
@@ -161,7 +162,7 @@ export default function createBucketLoader(
         createXliffLoader(),
         createFlatLoader(),
         createSyncLoader(),
-        createUnlocalizableLoader(options.isCacheRestore),
+        createUnlocalizableLoader(options.isCacheRestore, options.returnUnlocalizedKeys),
       );
     case "xml":
       return composeLoaders(
@@ -169,28 +170,28 @@ export default function createBucketLoader(
         createXmlLoader(),
         createFlatLoader(),
         createSyncLoader(),
-        createUnlocalizableLoader(options.isCacheRestore),
+        createUnlocalizableLoader(options.isCacheRestore, options.returnUnlocalizedKeys),
       );
     case "srt":
       return composeLoaders(
         createTextFileLoader(bucketPathPattern),
         createSrtLoader(),
         createSyncLoader(),
-        createUnlocalizableLoader(options.isCacheRestore),
+        createUnlocalizableLoader(options.isCacheRestore, options.returnUnlocalizedKeys),
       );
     case "dato":
       return composeLoaders(
         createDatoLoader(bucketPathPattern),
         createSyncLoader(),
         createFlatLoader(),
-        createUnlocalizableLoader(options.isCacheRestore),
+        createUnlocalizableLoader(options.isCacheRestore, options.returnUnlocalizedKeys),
       );
     case "vtt":
       return composeLoaders(
         createTextFileLoader(bucketPathPattern),
         createVttLoader(),
         createSyncLoader(),
-        createUnlocalizableLoader(options.isCacheRestore),
+        createUnlocalizableLoader(options.isCacheRestore, options.returnUnlocalizedKeys),
       );
     case "php":
       return composeLoaders(
@@ -198,7 +199,7 @@ export default function createBucketLoader(
         createPhpLoader(),
         createSyncLoader(),
         createFlatLoader(),
-        createUnlocalizableLoader(options.isCacheRestore),
+        createUnlocalizableLoader(options.isCacheRestore, options.returnUnlocalizedKeys),
       );
     case "vue-json":
       return composeLoaders(
@@ -206,7 +207,7 @@ export default function createBucketLoader(
         createVueJsonLoader(),
         createSyncLoader(),
         createFlatLoader(),
-        createUnlocalizableLoader(),
+        createUnlocalizableLoader(options.isCacheRestore, options.returnUnlocalizedKeys),
       );
   }
 }
diff --git a/packages/cli/src/cli/loaders/unlocalizable.spec.ts b/packages/cli/src/cli/loaders/unlocalizable.spec.ts
index cdb6c14f1..29ed846d1 100644
--- a/packages/cli/src/cli/loaders/unlocalizable.spec.ts
+++ b/packages/cli/src/cli/loaders/unlocalizable.spec.ts
@@ -16,30 +16,76 @@ describe("unlocalizable loader", () => {
     systemId: "Ab1cdefghijklmnopqrst2",
   };
 
-  describe.each([true, false])("cache restoration '%s'", (cacheRestoration) => {
-    it("should remove unlocalizable keys on pull", async () => {
-      const loader = createUnlocalizableLoader(cacheRestoration);
-      loader.setDefaultLocale("en");
-      const result = await loader.pull("en", data);
-
-      expect(result).toEqual({
-        foo: "bar",
-        numStr: "1.0",
-        boolStr: "false",
-        bar: "foo",
+  describe("cache restoration", () => {
+    describe.each([true, false])("%s", (cacheRestoration) => {
+      it("should remove unlocalizable keys on pull", async () => {
+        const loader = createUnlocalizableLoader(cacheRestoration);
+        loader.setDefaultLocale("en");
+        const result = await loader.pull("en", data);
+
+        expect(result).toEqual({
+          foo: "bar",
+          numStr: "1.0",
+          boolStr: "false",
+          bar: "foo",
+        });
+      });
+
+      it("should handle unlocalizable keys on push", async () => {
+        const pushData = { foo: "bar-es", bar: "foo-es" };
+
+        const loader = createUnlocalizableLoader(cacheRestoration);
+        loader.setDefaultLocale("en");
+        await loader.pull("en", data);
+        const result = await loader.push("es", pushData);
+
+        const expectedData = cacheRestoration ? { ...pushData } : { ...data, ...pushData };
+        expect(result).toEqual(expectedData);
       });
     });
+  });
 
-    it("should handle unlocalizable keys on push", async () => {
-      const pushData = { foo: "bar-es", bar: "foo-es" };
+  describe("return unlocalizable keys", () => {
+    describe.each([true, false])("%s", (returnUnlocalizedKeys) => {
+      it("should return unlocalizable keys on pull", async () => {
+        const loader = createUnlocalizableLoader(false, returnUnlocalizedKeys);
+        loader.setDefaultLocale("en");
+        const result = await loader.pull("en", data);
 
-      const loader = createUnlocalizableLoader(cacheRestoration);
-      loader.setDefaultLocale("en");
-      await loader.pull("en", data);
-      const result = await loader.push("es", pushData);
+        const extraUnlocalizableData = returnUnlocalizedKeys
+          ? {
+              unlocalizable: {
+                num: 1,
+                empty: "",
+                bool: true,
+                isoDate: "2025-02-21",
+                isoDateTime: "2025-02-21T00:00:00.000Z",
+                url: "https://example.com",
+                systemId: "Ab1cdefghijklmnopqrst2",
+              },
+            }
+          : {};
 
-      const expectedData = cacheRestoration ? { ...pushData } : { ...data, ...pushData };
-      expect(result).toEqual(expectedData);
+        expect(result).toEqual({
+          foo: "bar",
+          numStr: "1.0",
+          boolStr: "false",
+          bar: "foo",
+          ...extraUnlocalizableData,
+        });
+      });
+
+      it("should not affect push", async () => {
+        const pushData = { foo: "bar-es", bar: "foo-es" };
+
+        const loader = createUnlocalizableLoader(false, returnUnlocalizedKeys);
+        loader.setDefaultLocale("en");
+        await loader.pull("en", data);
+        const result = await loader.push("es", pushData);
+
+        const expectedData = { ...data, ...pushData };
+        expect(result).toEqual(expectedData);
+      });
     });
   });
 });
diff --git a/packages/cli/src/cli/loaders/unlocalizable.ts b/packages/cli/src/cli/loaders/unlocalizable.ts
index fea298521..06a962df5 100644
--- a/packages/cli/src/cli/loaders/unlocalizable.ts
+++ b/packages/cli/src/cli/loaders/unlocalizable.ts
@@ -7,6 +7,7 @@ import { createLoader } from "./_utils";
 
 export default function createUnlocalizableLoader(
   isCacheRestore: boolean = false,
+  returnUnlocalizedKeys: boolean = false,
 ): ILoader<Record<string, any>, Record<string, any>> {
   const rules = {
     isEmpty: (v: any) => _.isEmpty(v),
@@ -31,6 +32,11 @@ export default function createUnlocalizableLoader(
         .map(([key, _]) => key);
 
       const result = _.omitBy(input, (_, key) => passthroughKeys.includes(key));
+
+      if (returnUnlocalizedKeys) {
+        result.unlocalizable = _.omitBy(input, (_, key) => !passthroughKeys.includes(key));
+      }
+
       return result;
     },
     async push(locale, data, originalInput) {