diff --git a/lisa/_assets/kmodules/lisa/introspect_header.py b/lisa/_assets/kmodules/lisa/introspect_header.py
index 168ba9765c43ea2b8b1f915c71e8c5f4d1e38235..c173fb1e9d9f69dad477fc668f2cb59ee43669ff 100755
--- a/lisa/_assets/kmodules/lisa/introspect_header.py
+++ b/lisa/_assets/kmodules/lisa/introspect_header.py
@@ -31,6 +31,7 @@ import lisa._btf as btf
 
 
 def process_btf(out, path, introspect, internal_type_prefix, define_typ_names):
+    internal_type_prefix = internal_type_prefix or ''
     with open(path, 'rb') as f:
         data = f.read()