diff --git a/iopaint/model/brushnet/pipeline_brushnet.py b/iopaint/model/brushnet/pipeline_brushnet.py
index 2826e77..5f91f9d 100644
--- a/iopaint/model/brushnet/pipeline_brushnet.py
+++ b/iopaint/model/brushnet/pipeline_brushnet.py
@@ -201,7 +201,7 @@ class StableDiffusionBrushNetPipeline(
 
         if safety_checker is not None and feature_extractor is None:
             raise ValueError(
-                "Make sure to define a feature extractor when loading {self.__class__} if you want to use the safety"
+                f"Make sure to define a feature extractor when loading {self.__class__} if you want to use the safety"
                 " checker. If you do not want to use the safety checker, you can pass `'safety_checker=None'` instead."
             )
 
diff --git a/iopaint/model/power_paint/pipeline_powerpaint.py b/iopaint/model/power_paint/pipeline_powerpaint.py
index 13c1d27..7bb3f66 100644
--- a/iopaint/model/power_paint/pipeline_powerpaint.py
+++ b/iopaint/model/power_paint/pipeline_powerpaint.py
@@ -286,7 +286,7 @@ class StableDiffusionInpaintPipeline(
 
         if safety_checker is not None and feature_extractor is None:
             raise ValueError(
-                "Make sure to define a feature extractor when loading {self.__class__} if you want to use the safety"
+                f"Make sure to define a feature extractor when loading {self.__class__} if you want to use the safety"
                 " checker. If you do not want to use the safety checker, you can pass `'safety_checker=None'` instead."
             )
 
diff --git a/iopaint/model/power_paint/v2/pipeline_PowerPaint_Brushnet_CA.py b/iopaint/model/power_paint/v2/pipeline_PowerPaint_Brushnet_CA.py
index c1892e6..0a9cb6d 100644
--- a/iopaint/model/power_paint/v2/pipeline_PowerPaint_Brushnet_CA.py
+++ b/iopaint/model/power_paint/v2/pipeline_PowerPaint_Brushnet_CA.py
@@ -222,7 +222,7 @@ class StableDiffusionPowerPaintBrushNetPipeline(
 
         if safety_checker is not None and feature_extractor is None:
             raise ValueError(
-                "Make sure to define a feature extractor when loading {self.__class__} if you want to use the safety"
+                f"Make sure to define a feature extractor when loading {self.__class__} if you want to use the safety"
                 " checker. If you do not want to use the safety checker, you can pass `'safety_checker=None'` instead."
             )