diff --git a/src/main.py b/src/main.py
index d8fe3ea..e5064b6 100755
--- a/src/main.py
+++ b/src/main.py
@@ -771,6 +771,7 @@ def build_nexus_file(pld_fabrication, output_path="output/nffa-di_unnamed.h5"):
         rheed_data = pld_fabrication["rheed_data"]
         for layer in rheed_data:
             nx_rheed_layer = nx_rheed.create_group(layer)
+            nx_rheed_layer.attrs["NX_class"] = "NXsubentry"
 
             layer_dict = rheed_data[layer]
             n = layer_dict["layer_number"]