diff --git a/mlos_bench/mlos_bench/tunables/tunable_groups.py b/mlos_bench/mlos_bench/tunables/tunable_groups.py
index 74c3af91b4..452c13d95b 100644
--- a/mlos_bench/mlos_bench/tunables/tunable_groups.py
+++ b/mlos_bench/mlos_bench/tunables/tunable_groups.py
@@ -346,6 +346,12 @@ def assign(self, param_values: Mapping[str, TunableValue]) -> "TunableGroups":
         param_values : Mapping[str, TunableValue]
             Dictionary mapping Tunable parameter names to new values.
 
+            As a special behavior when the mapping is empty the method will restore
+            the default values rather than no-op.
+            This allows an empty dictionary in json configs to be used to reset the
+            tunables to defaults without having to copy the original values from the
+            tunable_params definition.
+
         Returns
         -------
         self : TunableGroups