diff --git a/python/boomer/common/cpp/rule_refinement.h b/python/boomer/common/cpp/rule_refinement.h
index 038c9c7372..77a84fce66 100644
--- a/python/boomer/common/cpp/rule_refinement.h
+++ b/python/boomer/common/cpp/rule_refinement.h
@@ -107,3 +107,7 @@ class ExactRuleRefinementImpl : virtual public IRuleRefinement {
                                   uint32 numLabelIndices, const uint32* labelIndices) override;
 
 };
+
+class ApproximateRuleRefinementImpl : virtual public IRuleRefinement {
+
+};