diff --git a/Source/driver/parse_castro_params.py b/Source/driver/parse_castro_params.py
index f2cc4d2472..9436a592f1 100755
--- a/Source/driver/parse_castro_params.py
+++ b/Source/driver/parse_castro_params.py
@@ -134,7 +134,7 @@ def write_headers_and_source(params, out_directory, struct_name):
     # output
 
     # find all the namespaces
-    namespaces = {q.namespace for q in params}
+    namespaces = sorted({q.namespace for q in params})
 
     for nm in sorted(namespaces):