diff --git a/src/lp/nack-header.hpp b/src/lp/nack-header.hpp
index 0c034f4..e4b8c14 100644
--- a/src/lp/nack-header.hpp
+++ b/src/lp/nack-header.hpp
@@ -46,6 +46,13 @@
 std::ostream&
 operator<<(std::ostream& os, NackReason reason);
 
+/** \brief compare NackReason for severity
+ *
+ *  lp::NackReason::NONE is treated as most severe
+ */
+bool
+isLessSevere(lp::NackReason x, lp::NackReason y);
+
 /**
  * \brief represents a Network NACK header
  */