diff --git a/src/ristretto255.h b/src/ristretto255.h
index 054b511..e2b350d 100644
--- a/src/ristretto255.h
+++ b/src/ristretto255.h
@@ -448,7 +448,10 @@ namespace ristretto255 {
 		}
 
 		template<typename T>
-		ristretto255::hsh<hashsize>& operator << (const T& j) {
+		typename std::enable_if< 
+		 	ro::is_serializable<const T>::value,
+			ristretto255::hsh<hashsize>& 
+		>::type operator << (const T& j) {
 			int i{ 1 };
 			if constexpr (std::is_same_v<std::remove_cvref_t<T>, std::span<const byte> >) {
 				i = crypto_generichash_blake2b_update(
@@ -464,7 +467,8 @@ namespace ristretto255 {
 					strlen(j) + 1
 				);
 			}
-			else if constexpr (is_serializable<const T>::value) {
+			else {
+				static_assert(is_serializable<const T>::value, "don't know a machine and compiler independent representation of this type");
 				auto sj = ro::serialize(j);
 				i = crypto_generichash_blake2b_update(
 					&(this->st),
@@ -472,9 +476,6 @@ namespace ristretto255 {
 					sj.size()
 				);
 			}
-			else {
-				static_assert(false, "don't know a machine and compiler independent representation of this type");
-			}
 			if (i) throw HashReuseException();
 			return *this;
 		}