diff --git a/app/Http/Controllers/Api/CountryController.php b/app/Http/Controllers/Api/CountryController.php
index 9cc24a1..51ee82d 100644
--- a/app/Http/Controllers/Api/CountryController.php
+++ b/app/Http/Controllers/Api/CountryController.php
@@ -33,10 +33,12 @@ class CountryController extends Controller
             )
             ->when(
                 $request->exists('selected'),
-                fn (Builder $query) => $query
-                    ->whereIn('code', $request->input('selected', []))
-                    ->orWhereIn('id',
-                        $request->input('selected', [])),
+                function (Builder $query) use ($request) {
+                    $selected = $request->input('selected', []);
+
+                    $query->whereIn('code', $selected)
+                        ->orWhereIn('id', array_filter($selected, 'is_numeric'));
+                },
                 fn (Builder $query) => $query->limit(10),
             )
             ->get()
diff --git a/tests/Feature/Api/CountryControllerTest.php b/tests/Feature/Api/CountryControllerTest.php
new file mode 100644
index 0000000..7018c94
--- /dev/null
+++ b/tests/Feature/Api/CountryControllerTest.php
@@ -0,0 +1,13 @@
+<?php
+
+use App\Models\Country;
+
+it('does not crash when selected contains non-numeric codes', function () {
+    Country::factory()->create(['code' => 'CH']);
+
+    $response = $this->getJson('/api/countries?'.http_build_query([
+        'selected' => ['CH', 'de', '1'],
+    ]));
+
+    $response->assertSuccessful();
+});