diff --git a/src/snark/libsnark/algebra/fields/fp.hpp b/src/snark/libsnark/algebra/fields/fp.hpp
index ef145b5ac..af9eb0b9a 100644
--- a/src/snark/libsnark/algebra/fields/fp.hpp
+++ b/src/snark/libsnark/algebra/fields/fp.hpp
@@ -67,7 +67,7 @@ public:
 
     Fp_model() {};
     Fp_model(const bigint<n> &b);
-    Fp_model(const long x, const bool is_unsigned=false);
+    Fp_model(const int64_t x, const bool is_unsigned=false);
 
     void set_uint64(const uint64_t x);
 
diff --git a/src/snark/libsnark/algebra/fields/fp.tcc b/src/snark/libsnark/algebra/fields/fp.tcc
index 7556e0140..d38905b1c 100644
--- a/src/snark/libsnark/algebra/fields/fp.tcc
+++ b/src/snark/libsnark/algebra/fields/fp.tcc
@@ -194,7 +194,7 @@ Fp_model<n,modulus>::Fp_model(const bigint<n> &b)
 }
 
 template<mp_size_t n, const bigint<n>& modulus>
-Fp_model<n,modulus>::Fp_model(const long x, const bool is_unsigned)
+Fp_model<n,modulus>::Fp_model(const int64_t x, const bool is_unsigned)
 {
     if (is_unsigned || x >= 0)
     {