diff --git a/apps/graph/storage_cartesian_function_store.cpp b/apps/graph/storage_cartesian_function_store.cpp
index 3f5b734e0..be6649b9a 100644
--- a/apps/graph/storage_cartesian_function_store.cpp
+++ b/apps/graph/storage_cartesian_function_store.cpp
@@ -12,18 +12,20 @@ namespace Graph {
 StorageCartesianFunctionStore::StorageCartesianFunctionStore() :
   Shared::StorageFunctionStore()
 {
-  addEmptyModel();
+  Ion::Storage::Record::ErrorStatus error = addEmptyModel();
+  assert(error == Ion::Storage::Record::ErrorStatus::None);
 }
 
 void StorageCartesianFunctionStore::removeAll() {
   StorageFunctionStore::removeAll();
-  addEmptyModel();
+  Ion::Storage::Record::ErrorStatus error = addEmptyModel();
+  assert(error == Ion::Storage::Record::ErrorStatus::None);
 }
 
-void StorageCartesianFunctionStore::addEmptyModel() {
+Ion::Storage::Record::ErrorStatus StorageCartesianFunctionStore::addEmptyModel() {
   Ion::Storage::Record::ErrorStatus error;
   StorageCartesianFunction newModel = StorageCartesianFunction::NewModel(&error);
-  assert(error == Ion::Storage::Record::ErrorStatus::None);
+  return error;
 }
 
 void StorageCartesianFunctionStore::privateSetMemoizedModelAtIndex(int cacheIndex, Ion::Storage::Record record) const {
diff --git a/apps/graph/storage_cartesian_function_store.h b/apps/graph/storage_cartesian_function_store.h
index 02ca4ae9f..1d5c080a9 100644
--- a/apps/graph/storage_cartesian_function_store.h
+++ b/apps/graph/storage_cartesian_function_store.h
@@ -17,7 +17,7 @@ public:
   char symbol() const override { return 'x'; }
   void removeAll() override;
 private:
-  void addEmptyModel();
+  Ion::Storage::Record::ErrorStatus addEmptyModel() override;
   const char * modelExtension() const override { return Shared::GlobalContext::funcExtension; }
   void privateSetMemoizedModelAtIndex(int cacheIndex, Ion::Storage::Record record) const override;
   void moveMemoizedModel(int previousIndex, int nextIndex) const override;
diff --git a/apps/shared/storage_expression_model_store.h b/apps/shared/storage_expression_model_store.h
index db157c663..5b5c63cd2 100644
--- a/apps/shared/storage_expression_model_store.h
+++ b/apps/shared/storage_expression_model_store.h
@@ -21,6 +21,7 @@ public:
   virtual StorageExpressionModel * definedModelAtIndex(int i) const;
 
   // Add and Remove
+  virtual Ion::Storage::Record::ErrorStatus addEmptyModel() = 0;
   virtual void removeAll();
   void removeModel(StorageExpressionModel * f);