diff --git a/pyext/ctools/__init__.py b/pyext/ctools/__init__.py
index 9c86e0f..ce53507 100644
--- a/pyext/ctools/__init__.py
+++ b/pyext/ctools/__init__.py
@@ -1,3 +1,6 @@
+# import gammalib first
+import gammalib
+
 # Import sub modules
 from .tools import *
 #import obsutils (require explicit from ctools import obsutils)