diff --git a/include/ipmid/message/unpack.hpp b/include/ipmid/message/unpack.hpp
index 4ac4916..3a80c3f 100644
--- a/include/ipmid/message/unpack.hpp
+++ b/include/ipmid/message/unpack.hpp
@@ -157,7 +157,7 @@
 
 /** @brief Specialization of UnpackSingle for fixed_uint_t types
  */
-template <unsigned N>
+template <bitcount_t N>
 struct UnpackSingle<fixed_uint_t<N>>
 {
     static int op(Payload& p, fixed_uint_t<N>& t)