diff --git a/ethosu/vela/architecture_features.py b/ethosu/vela/architecture_features.py
index 822bc11..021597e 100644
--- a/ethosu/vela/architecture_features.py
+++ b/ethosu/vela/architecture_features.py
@@ -268,6 +268,7 @@
         }
 
         self.tensor_storage_mem_type = {
+            TensorPurpose.Unknown: MemType.Unknown,
             TensorPurpose.Weights: MemType.Permanent_NPU,
             TensorPurpose.FeatureMap: MemType.Scratch,
             TensorPurpose.LUT: MemType.Scratch,