diff --git a/cwl/cwl_app/__init__.py b/cwl/cwl_app/__init__.py
index 9f61e51..d418f32 100644
--- a/cwl/cwl_app/__init__.py
+++ b/cwl/cwl_app/__init__.py
@@ -1,3 +1,5 @@
 """This package provides a CWLApp class to run CWL Command Line Tools."""
 
-from cwl.cwl_app import CWLApp
\ No newline at end of file
+from cwl.cwl_app import CWLApp
+
+__all__ = ['CWLApp']
\ No newline at end of file