diff --git a/python/python/ert_gui/simulation/models/multiple_data_assimilation.py b/python/python/ert_gui/simulation/models/multiple_data_assimilation.py
index 984f033983a..5aeb2814212 100644
--- a/python/python/ert_gui/simulation/models/multiple_data_assimilation.py
+++ b/python/python/ert_gui/simulation/models/multiple_data_assimilation.py
@@ -83,7 +83,7 @@ def count_active_realizations(self, run_context):
 
 
     def update(self, run_context, weight):
-        source_fs = run_context.get_result_fs( )
+        source_fs = run_context.get_sim_fs( )
         next_iteration = run_context.get_iter( ) + 1
         target_fs = run_context.get_target_fs( )