diff --git a/src/Exception/UnsupportedIndexLanguageException.php b/src/Exception/UnsupportedIndexLanguageException.php
new file mode 100644
index 0000000..8676722
--- /dev/null
+++ b/src/Exception/UnsupportedIndexLanguageException.php
@@ -0,0 +1,35 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Atoolo\Search\Exception;
+
+use Atoolo\Resource\ResourceLanguage;
+use RuntimeException;
+
+class UnsupportedIndexLanguageException extends RuntimeException
+{
+    public function __construct(
+        private readonly string $index,
+        private readonly ResourceLanguage $lang,
+        string $message = "",
+        int $code = 0,
+        ?\Throwable $previous = null
+    ) {
+        parent::__construct(
+            $index . '/' . $lang->code . ': ' . $message,
+            $code,
+            $previous
+        );
+    }
+
+    public function getIndex(): string
+    {
+        return $this->index;
+    }
+
+    public function getLang(): ResourceLanguage
+    {
+        return $this->lang;
+    }
+}
diff --git a/src/Service/IndexName.php b/src/Service/IndexName.php
index 2fe9163..1d3ac99 100644
--- a/src/Service/IndexName.php
+++ b/src/Service/IndexName.php
@@ -5,9 +5,14 @@
 namespace Atoolo\Search\Service;
 
 use Atoolo\Resource\ResourceLanguage;
+use Atoolo\Search\Exception\UnsupportedIndexLanguageException;
 
 interface IndexName
 {
+    /**
+     * @throws UnsupportedIndexLanguageException Is thrown if no valid index
+     *  can be determined for the language.
+     */
     public function name(ResourceLanguage $lang): string;
 
     /**
diff --git a/src/Service/Indexer/InternalResourceIndexer.php b/src/Service/Indexer/InternalResourceIndexer.php
index 3547f60..c633042 100644
--- a/src/Service/Indexer/InternalResourceIndexer.php
+++ b/src/Service/Indexer/InternalResourceIndexer.php
@@ -10,6 +10,7 @@
 use Atoolo\Resource\ResourceLocation;
 use Atoolo\Search\Dto\Indexer\IndexerParameter;
 use Atoolo\Search\Dto\Indexer\IndexerStatus;
+use Atoolo\Search\Exception\UnsupportedIndexLanguageException;
 use Atoolo\Search\Indexer;
 use Exception;
 use Psr\Log\LoggerInterface;
@@ -248,23 +249,19 @@ private function indexTranslationSplittedResources(
         );
 
         foreach ($splitterResult->getLanguages() as $lang) {
-            $langIndex = $this->indexService->getIndex($lang);
-
-            if ($index === $langIndex) {
-                $this->handleError(
-                    'No Index for language "' . $lang->code . '" ' .
-                    'found (base index: "' . $index . '")'
+            try {
+                $langIndex = $this->indexService->getIndex($lang);
+                $this->indexResourcesPerLanguageIndex(
+                    $processId,
+                    $parameter,
+                    $lang,
+                    $langIndex,
+                    $splitterResult->getTranslations($lang)
                 );
+            } catch (UnsupportedIndexLanguageException $e) {
+                $this->handleError($e->getMessage());
                 continue;
             }
-
-            $this->indexResourcesPerLanguageIndex(
-                $processId,
-                $parameter,
-                $lang,
-                $langIndex,
-                $splitterResult->getTranslations($lang)
-            );
         }
     }
 
diff --git a/src/Service/ResourceChannelBasedIndexName.php b/src/Service/ResourceChannelBasedIndexName.php
index f481dcc..dabf43a 100644
--- a/src/Service/ResourceChannelBasedIndexName.php
+++ b/src/Service/ResourceChannelBasedIndexName.php
@@ -6,6 +6,7 @@
 
 use Atoolo\Resource\ResourceChannel;
 use Atoolo\Resource\ResourceLanguage;
+use Atoolo\Search\Exception\UnsupportedIndexLanguageException;
 
 class ResourceChannelBasedIndexName implements IndexName
 {
@@ -14,12 +15,17 @@ public function __construct(
     ) {
     }
 
+    /**
+     * @throws UnsupportedIndexLanguageException
+     */
     public function name(ResourceLanguage $lang): string
     {
         $locale = $this->langToAvailableLocale($this->resourceChannel, $lang);
+
         if (empty($locale)) {
             return $this->resourceChannel->searchIndex;
         }
+
         return $this->resourceChannel->searchIndex . '-' . $locale;
     }
 
@@ -40,6 +46,9 @@ public function names(): array
         return $names;
     }
 
+    /**
+     * @throws UnsupportedIndexLanguageException
+     */
     private function langToAvailableLocale(
         ResourceChannel $resourceChannel,
         ResourceLanguage $lang
@@ -56,6 +65,11 @@ private function langToAvailableLocale(
                 return $availableLocale;
             }
         }
-        return '';
+        throw new UnsupportedIndexLanguageException(
+            $resourceChannel->searchIndex,
+            $lang,
+            'No valid index can be determined for the language ' .
+            $lang->code
+        );
     }
 }
diff --git a/test/Exception/UnsupportedIndexLanguageExceptionTest.php b/test/Exception/UnsupportedIndexLanguageExceptionTest.php
new file mode 100644
index 0000000..f72b9d1
--- /dev/null
+++ b/test/Exception/UnsupportedIndexLanguageExceptionTest.php
@@ -0,0 +1,38 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Atoolo\Search\Test\Exception;
+
+use Atoolo\Resource\ResourceLanguage;
+use Atoolo\Search\Exception\UnsupportedIndexLanguageException;
+use PHPUnit\Framework\TestCase;
+
+class UnsupportedIndexLanguageExceptionTest extends TestCase
+{
+    public function testGetIndex(): void
+    {
+        $e = new UnsupportedIndexLanguageException(
+            'test',
+            ResourceLanguage::of('de')
+        );
+        $this->assertEquals(
+            'test',
+            $e->getIndex(),
+            'unexpected index'
+        );
+    }
+
+    public function testGetLang(): void
+    {
+        $e = new UnsupportedIndexLanguageException(
+            'test',
+            ResourceLanguage::of('de')
+        );
+        $this->assertEquals(
+            ResourceLanguage::of('de'),
+            $e->getLang(),
+            'unexpected index'
+        );
+    }
+}
diff --git a/test/Service/Indexer/InternalResourceIndexerTest.php b/test/Service/Indexer/InternalResourceIndexerTest.php
index 2f884ce..b55cf3f 100644
--- a/test/Service/Indexer/InternalResourceIndexerTest.php
+++ b/test/Service/Indexer/InternalResourceIndexerTest.php
@@ -8,6 +8,7 @@
 use Atoolo\Resource\ResourceLoader;
 use Atoolo\Resource\ResourceLocation;
 use Atoolo\Search\Dto\Indexer\IndexerConfiguration;
+use Atoolo\Search\Exception\UnsupportedIndexLanguageException;
 use Atoolo\Search\Service\Indexer\DocumentEnricher;
 use Atoolo\Search\Service\Indexer\IndexerConfigurationLoader;
 use Atoolo\Search\Service\Indexer\IndexerProgressHandler;
@@ -117,6 +118,13 @@ public function setUp(): void
                 if ($lang->code === 'en') {
                     return 'test-en_US';
                 }
+                if ($lang->code === 'fr') {
+                    throw new UnsupportedIndexLanguageException(
+                        'test',
+                        $lang,
+                        'unsupported language'
+                    );
+                }
                 return 'test';
             });
         $this->solrIndexService->method('updater')
diff --git a/test/Service/ResourceChannelBasedIndexNameTest.php b/test/Service/ResourceChannelBasedIndexNameTest.php
index 84a501b..9f5b1dd 100644
--- a/test/Service/ResourceChannelBasedIndexNameTest.php
+++ b/test/Service/ResourceChannelBasedIndexNameTest.php
@@ -6,6 +6,7 @@
 
 use Atoolo\Resource\ResourceChannel;
 use Atoolo\Resource\ResourceLanguage;
+use Atoolo\Search\Exception\UnsupportedIndexLanguageException;
 use Atoolo\Search\Service\ResourceChannelBasedIndexName;
 use PHPUnit\Framework\Attributes\CoversClass;
 use PHPUnit\Framework\TestCase;
@@ -58,12 +59,8 @@ public function testNameWithLang(): void
 
     public function testNameWithUnsupportedLang(): void
     {
-        $this->assertEquals(
-            'test',
-            $this->indexName->name(ResourceLanguage::of('it')),
-            'The default index name should be returned ' .
-            'if the language is not supported'
-        );
+        $this->expectException(UnsupportedIndexLanguageException::class);
+        $this->indexName->name(ResourceLanguage::of('it'));
     }
 
     public function testNames(): void