diff --git a/README.md b/README.md
index 4eef89f..ce14cd2 100644
--- a/README.md
+++ b/README.md
@@ -6,7 +6,7 @@ Cryptocurrencies portfolio manager.
 
 * MySQL
 * C++ REST SDK : https://github.com/Microsoft/cpprestsdk
-* OpenSSL
+* OpenSSL (1.1.0+)
 * GMP
 * Boost
 * sqlpp11 (modified to handle decimal type) : https://github.com/evilny0/sqlpp11/tree/decimal
diff --git a/src/exchanges/kraken.cpp b/src/exchanges/kraken.cpp
index 90bb138..e118193 100644
--- a/src/exchanges/kraken.cpp
+++ b/src/exchanges/kraken.cpp
@@ -222,14 +222,13 @@ vector<unsigned char> ExchangeHandlerKraken::hmac_sha512(const vector<unsigned c
     unsigned int len = EVP_MAX_MD_SIZE;
     vector<unsigned char> digest(len);
 
-    HMAC_CTX ctx;
-    HMAC_CTX_init(&ctx);
+    HMAC_CTX* ctx = HMAC_CTX_new();
 
-    HMAC_Init_ex(&ctx, key.data(), key.size(), EVP_sha512(), NULL);
-    HMAC_Update(&ctx, data.data(), data.size());
-    HMAC_Final(&ctx, digest.data(), &len);
+    HMAC_Init_ex(ctx, key.data(), key.size(), EVP_sha512(), NULL);
+    HMAC_Update(ctx, data.data(), data.size());
+    HMAC_Final(ctx, digest.data(), &len);
 
-    HMAC_CTX_cleanup(&ctx);
+    HMAC_CTX_free(ctx);
 
     return digest;
 }