diff --git a/src/controllers/api/translate.ts b/src/controllers/api/translate.ts
index f2ca9eae..e1577478 100644
--- a/src/controllers/api/translate.ts
+++ b/src/controllers/api/translate.ts
@@ -132,7 +132,10 @@ const translateController: AppController = async (c) => {
 
     dittoTranslations.set(translatedId, { data: mastodonTranslation });
     return c.json(mastodonTranslation, 200);
-  } catch {
+  } catch (e) {
+    if (e instanceof Error && e.message?.includes('not supported')) {
+      return c.json({ error: `Translation of source language '${event.language}' not supported` }, 422);
+    }
     return c.json({ error: 'Service Unavailable' }, 503);
   }
 };
diff --git a/src/translators/DeepLTranslator.ts b/src/translators/DeepLTranslator.ts
index d97c59a1..5c457903 100644
--- a/src/translators/DeepLTranslator.ts
+++ b/src/translators/DeepLTranslator.ts
@@ -68,6 +68,9 @@ export class DeepLTranslator implements DittoTranslator {
 
     const response = await this.fetch(request);
     const json = await response.json();
+    if (!response.ok) {
+      throw new Error(json['message']);
+    }
     const data = DeepLTranslator.schema().parse(json);
 
     return data;
diff --git a/src/translators/LibreTranslateTranslator.ts b/src/translators/LibreTranslateTranslator.ts
index d632c71e..a7d4eb85 100644
--- a/src/translators/LibreTranslateTranslator.ts
+++ b/src/translators/LibreTranslateTranslator.ts
@@ -68,6 +68,9 @@ export class LibreTranslateTranslator implements DittoTranslator {
 
     const response = await this.fetch(request);
     const json = await response.json();
+    if (!response.ok) {
+      throw new Error(json['error']);
+    }
     const data = LibreTranslateTranslator.schema().parse(json);
 
     return data;