diff --git a/doc/erko_howto_tools.txt b/doc/erko_howto_tools.txt
index e0f686325f50276cecd6b064bb34e136af15dd43..7148cb3dfd19dba0805f1b9baf7c3bbb1de40a8e 100755
--- a/doc/erko_howto_tools.txt
+++ b/doc/erko_howto_tools.txt
@@ -1591,6 +1591,13 @@ Check of SDPTR op dop369 actief is met:
 > uals -u 10.87.2.36:4840 -p "0:Objects"
 
 
+# Add rtdsp module path to $PYTHONPATH in a cell
+import os
+import sys
+module_path = os.path.abspath(os.path.join('../'))
+if module_path not in sys.path:
+    sys.path.insert(0, module_path)
+
 *******************************************************************************
 * Graphana
 *******************************************************************************