diff --git a/src/crypto/crypto-sugar.h b/src/crypto/crypto-sugar.h
index 1caf06f0..0c8f9dd9 100644
--- a/src/crypto/crypto-sugar.h
+++ b/src/crypto/crypto-sugar.h
@@ -1,5 +1,5 @@
-// Copyright (c) 2020-2022 Zano Project
-// Copyright (c) 2020-2022 sowle (val@zano.org, crypto.sowle@gmail.com)
+// Copyright (c) 2020-2023 Zano Project
+// Copyright (c) 2020-2023 sowle (val@zano.org, crypto.sowle@gmail.com)
 // Distributed under the MIT/X11 software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 //
@@ -309,6 +309,14 @@ namespace crypto
       return *this;
     }
 
+    scalar_t operator-() const
+    {
+      static unsigned char zero[32] = { 0 };
+      scalar_t result;
+      sc_sub(&result.m_s[0], zero, &m_s[0]);
+      return result;
+    }
+
     // returns this = a * b
     scalar_t& assign_mul(const scalar_t& a, const scalar_t& b)
     {
diff --git a/tests/functional_tests/crypto_tests.cpp b/tests/functional_tests/crypto_tests.cpp
index 74ca3425..77a0cfa4 100644
--- a/tests/functional_tests/crypto_tests.cpp
+++ b/tests/functional_tests/crypto_tests.cpp
@@ -823,13 +823,18 @@ TEST(crypto, keys)
 
 TEST(crypto, scalar_basics)
 {
-  scalar_t zero = 0;
+  const scalar_t zero = 0;
   ASSERT_TRUE(zero.is_zero());
-  scalar_t one = 1;
+  const scalar_t one = 1;
   ASSERT_FALSE(one.is_zero());
   ASSERT_TRUE(one > zero);
   ASSERT_TRUE(one.muladd(zero, zero) == zero);
 
+  ASSERT_EQ(-one, c_scalar_Lm1);
+  ASSERT_EQ(-one, scalar_t(0) - one);
+  ASSERT_EQ(-zero, zero);
+  ASSERT_EQ(-c_scalar_Lm1, one);
+
   scalar_t z = 0;
   for (size_t j = 0; j < 1000; ++j)
   {