diff --git a/dist/openclaw/toolkit/image_gen.py b/dist/openclaw/toolkit/image_gen.py
index 3783dfd..a59b317 100644
--- a/dist/openclaw/toolkit/image_gen.py
+++ b/dist/openclaw/toolkit/image_gen.py
@@ -259,7 +259,7 @@ class GeminiProvider(ImageProvider):
             inline_data = part.get("inlineData")
             if inline_data and inline_data.get("mimeType", "").startswith("image/"):
                 return base64.b64decode(inline_data["data"])
-        raise ValueError(f"No image found in Gemini response parts")
+        raise ValueError("No image found in Gemini response parts")
 
 
 # --- Provider registry ---
@@ -270,6 +270,7 @@ PROVIDERS = {
     "gemini": GeminiProvider,
 }
 
+
 def _build_provider(config: dict) -> ImageProvider:
     """Build an ImageProvider from config.yaml's image section."""
     img_cfg = config.get("image", {})