diff --git a/invokeai/app/invocations/denoise_latents.py b/invokeai/app/invocations/denoise_latents.py
index b7a296a9b4..c502234e5e 100644
--- a/invokeai/app/invocations/denoise_latents.py
+++ b/invokeai/app/invocations/denoise_latents.py
@@ -775,6 +775,10 @@ class DenoiseLatentsInvocation(BaseInvocation):
 
         ### inpaint
         mask, masked_latents, is_gradient_mask = self.prep_inpaint_mask(context, latents)
+        # NOTE: We used to identify inpainting models by inpecting the shape of the loaded UNet model weights. Now we
+        # use the ModelVariantType config. During testing, there was a report of a user with models that had an
+        # incorrect ModelVariantType value. Re-installing the model fixed the issue. If this issue turns out to be
+        # prevalent, we will have to revisit how we initialize the inpainting extensions.
         if unet_config.variant == ModelVariantType.Inpaint:
             ext_manager.add_extension(InpaintModelExt(mask, masked_latents, is_gradient_mask))
         elif mask is not None:
@@ -830,6 +834,8 @@ class DenoiseLatentsInvocation(BaseInvocation):
         seed, noise, latents = self.prepare_noise_and_latents(context, self.noise, self.latents)
 
         mask, masked_latents, gradient_mask = self.prep_inpaint_mask(context, latents)
+        # At this point, the mask ranges from 0 (leave unchanged) to 1 (inpaint).
+        # We invert the mask here for compatibility with the old backend implementation.
         if mask is not None:
             mask = 1 - mask
 
diff --git a/invokeai/backend/stable_diffusion/extensions/inpaint.py b/invokeai/backend/stable_diffusion/extensions/inpaint.py
index 7bdd9238df..437e06df76 100644
--- a/invokeai/backend/stable_diffusion/extensions/inpaint.py
+++ b/invokeai/backend/stable_diffusion/extensions/inpaint.py
@@ -75,7 +75,11 @@ class InpaintExt(ExtensionBase):
     @callback(ExtensionCallbackType.PRE_DENOISE_LOOP)
     def init_tensors(self, ctx: DenoiseContext):
         if not self._is_normal_model(ctx.unet):
-            raise ValueError("InpaintExt should be used only on normal models!")
+            raise ValueError(
+                "InpaintExt should be used only on normal (non-inpainting) models. This could be caused by an "
+                "inpainting model that was incorrectly marked as a non-inpainting model. In some cases, this can be "
+                "fixed by removing and re-adding the model (so that it gets re-probed)."
+            )
 
         self._mask = self._mask.to(device=ctx.latents.device, dtype=ctx.latents.dtype)