diff --git a/ethosu/vela/architecture_features.py b/ethosu/vela/architecture_features.py
index b59122e..f1cabdd 100644
--- a/ethosu/vela/architecture_features.py
+++ b/ethosu/vela/architecture_features.py
@@ -243,6 +243,7 @@
 
         self.tensor_storage_mem_area = {
             # permanent mem_area
+            TensorPurpose.Unknown: MemArea.Unknown,
             TensorPurpose.Weights: self.permanent_storage_mem_area,
             TensorPurpose.FeatureMap: self.feature_map_storage_mem_area,
         }