diff --git a/force_bdss/mco/parameters/core_mco_parameters.py b/force_bdss/mco/parameters/core_mco_parameters.py
index e33559151c8ac348d846bc19a55387249f242d37..fafb09875d263b2a6504ecbc185ba75848242fca 100644
--- a/force_bdss/mco/parameters/core_mco_parameters.py
+++ b/force_bdss/mco/parameters/core_mco_parameters.py
@@ -10,8 +10,8 @@ class RangedMCOParameter(BaseMCOParameter):
     """Expresses a MCO parameter that has a range between two floating
     point values."""
     initial_value = Float()
-    upper_bound = Float()
     lower_bound = Float()
+    upper_bound = Float(1)
 
 
 class RangedMCOParameterFactory(BaseMCOParameterFactory):