diff --git a/src/common_models/interfaces.jl b/src/common_models/interfaces.jl
index f52e2da1..77d9e3e3 100644
--- a/src/common_models/interfaces.jl
+++ b/src/common_models/interfaces.jl
@@ -206,6 +206,8 @@ end
 """
 Extension point: Calculate auxiliary variable values.
 Concrete implementations in PowerOperationsModels for specific aux variable types.
+Evaluator-bound aux variables get the `AbstractEvaluationData` that produced them
+as a fourth argument, so the implementation does not have to look it up.
 """
 function calculate_aux_variable_value! end
 
diff --git a/src/core/optimization_container.jl b/src/core/optimization_container.jl
index ca1fb9f6..9841558c 100644
--- a/src/core/optimization_container.jl
+++ b/src/core/optimization_container.jl
@@ -1332,7 +1332,7 @@ function calculate_aux_variables!(
             @debug "Processing evaluator $(T)"
             evaluate!(data, container, system)
             for key in evaluator_aux_var_keys
-                calculate_aux_variable_value!(container, key, system)
+                calculate_aux_variable_value!(container, key, system, data)
             end
         end
     end