diff --git a/mtenn/config.py b/mtenn/config.py
index 48c3577..0808a19 100644
--- a/mtenn/config.py
+++ b/mtenn/config.py
@@ -82,7 +82,7 @@ class CombinationConfig(StringEnum):
 
 
 class ModelConfigBase(BaseModel):
-    model_type: ClassVar[ModelType.INVALID] = ModelType.INVALID
+    model_type: ModelType = Field(ModelType.INVALID, const=True, allow_mutation=False)
 
     # Shared parameters for MTENN
     grouped: bool = Field(False, description="Model is a grouped (multi-pose) model.")
@@ -172,6 +172,9 @@ class ModelConfigBase(BaseModel):
         ),
     )
 
+    class Config:
+        validate_assignment = True
+
     @abc.abstractmethod
     def _build(self, mtenn_params={}) -> mtenn.model.Model:
         ...
@@ -275,7 +278,7 @@ class GATModelConfig(ModelConfigBase):
         "biases": bool,
     }
 
-    model_type: ClassVar[ModelType.GAT] = ModelType.GAT
+    model_type: ModelType = Field(ModelType.GAT, const=True)
 
     in_feats: int = Field(
         CanonicalAtomFeaturizer().feat_size(),
@@ -479,7 +482,7 @@ class SchNetModelConfig(ModelConfigBase):
     given in PyG.
     """
 
-    model_type: ClassVar[ModelType.schnet] = ModelType.schnet
+    model_type: ModelType = Field(ModelType.schnet, const=True)
 
     hidden_channels: int = Field(128, description="Hidden embedding size.")
     num_filters: int = Field(
@@ -601,7 +604,7 @@ class E3NNModelConfig(ModelConfigBase):
     Class for constructing an e3nn ML model.
     """
 
-    model_type: ClassVar[ModelType.e3nn] = ModelType.e3nn
+    model_type: ModelType = Field(ModelType.e3nn, const=True)
 
     num_atom_types: int = Field(
         100,