diff --git a/galois_field.hh b/galois_field.hh
index 1ab1f8b..d6e3086 100644
--- a/galois_field.hh
+++ b/galois_field.hh
@@ -171,6 +171,18 @@ Value<M, POLY, TYPE> operator + (Value<M, POLY, TYPE> a, Value<M, POLY, TYPE> b)
 	return Value<M, POLY, TYPE>(a.v ^ b.v);
 }
 
+template <int M, int POLY, typename TYPE>
+Value<M, POLY, TYPE> operator - (Value<M, POLY, TYPE> a)
+{
+	return a;
+}
+
+template <int M, int POLY, typename TYPE>
+Value<M, POLY, TYPE> operator - (Value<M, POLY, TYPE> a, Value<M, POLY, TYPE> b)
+{
+	return a + b;
+}
+
 template <int M, int POLY, typename TYPE>
 Index<M, POLY, TYPE> operator * (Index<M, POLY, TYPE> a, Index<M, POLY, TYPE> b)
 {