diff --git a/RATapi/inputs.py b/RATapi/inputs.py
index 06d9f82c..e362cf6d 100644
--- a/RATapi/inputs.py
+++ b/RATapi/inputs.py
@@ -179,7 +179,7 @@ def make_problem(project: RATapi.Project) -> ProblemDefinition:
     for layer in project.layers:
         layer_params = [
             project.parameters.index(getattr(layer, attribute), True)
-            for attribute in list(layer.model_fields.keys())[1:-2]
+            for attribute in list(RATapi.models.Layer.model_fields.keys())[1:-2]
         ]
         layer_params.append(project.parameters.index(layer.hydration, True) if layer.hydration else float("NaN"))
         layer_params.append(hydrate_id[layer.hydrate_with])
diff --git a/RATapi/project.py b/RATapi/project.py
index ae2ed2cc..0dfbd0a5 100644
--- a/RATapi/project.py
+++ b/RATapi/project.py
@@ -365,12 +365,12 @@ def model_post_init(self, __context: Any) -> None:
         and wrap ClassList routines to control revalidation.
         """
         # Ensure all ClassLists have the correct _class_handle defined
-        for field in (fields := self.model_fields):
-            type = fields[field].annotation
-            if get_origin(type) == ClassList:
+        for field in (fields := Project.model_fields):
+            annotation = fields[field].annotation
+            if get_origin(annotation) == ClassList:
                 classlist = getattr(self, field)
                 if not hasattr(field, "_class_handle"):
-                    classlist._class_handle = get_args(type)[0]
+                    classlist._class_handle = get_args(annotation)[0]
 
         layers_field = self.layers
         if not hasattr(layers_field, "_class_handle"):
diff --git a/tests/test_project.py b/tests/test_project.py
index e82a84da..c0e26685 100644
--- a/tests/test_project.py
+++ b/tests/test_project.py
@@ -141,7 +141,7 @@ def test_classlists(test_project) -> None:
     """The ClassLists in the "Project" model should contain instances of the models given by the dictionary
     "model_in_classlist".
     """
-    for model in (fields := test_project.model_fields):
+    for model in (fields := RATapi.Project.model_fields):
         if get_origin(fields[model].annotation) == RATapi.ClassList:
             class_list = getattr(test_project, model)
             assert class_list._class_handle == get_args(fields[model].annotation)[0]
@@ -1613,7 +1613,7 @@ def test_save_load(project, request):
     for file in original_project.custom_files:
         file.path = file.path.resolve()
 
-    for field in original_project.model_fields:
+    for field in RATapi.Project.model_fields:
         assert getattr(converted_project, field) == getattr(original_project, field)