diff --git a/src/Cpu.cpp b/src/Cpu.cpp
index eba993b37..f8fb092ca 100644
--- a/src/Cpu.cpp
+++ b/src/Cpu.cpp
@@ -4,8 +4,8 @@
  * Copyright 2014      Lucas Jones <https://github.com/lucasjones>
  * Copyright 2014-2016 Wolf9466    <https://github.com/OhGodAPet>
  * Copyright 2016      Jay D Dee   <jayddee246@gmail.com>
- * Copyright 2016-2017 XMRig       <support@xmrig.com>
- *
+ * Copyright 2017-2018 XMR-Stak    <https://github.com/fireice-uk>, <https://github.com/psychocrypt>
+ * Copyright 2016-2018 XMRig       <https://github.com/xmrig>, <support@xmrig.com>
  *
  *   This program is free software: you can redistribute it and/or modify
  *   it under the terms of the GNU General Public License as published by
@@ -39,7 +39,7 @@ int Cpu::m_totalCores    = 0;
 int Cpu::m_totalThreads  = 0;
 
 
-int Cpu::optimalThreadsCount(int algo, bool doubleHash, int maxCpuUsage)
+int Cpu::optimalThreadsCount(xmrig::Algo algo, bool doubleHash, int maxCpuUsage)
 {
     if (m_totalThreads == 1) {
         return 1;
@@ -54,7 +54,18 @@ int Cpu::optimalThreadsCount(int algo, bool doubleHash, int maxCpuUsage)
     }
 
     int count = 0;
-    const int size = (algo ? 1024 : 2048) * (doubleHash ? 2 : 1);
+    int size  = 2048;
+
+    if (algo == xmrig::CRYPTONIGHT_LITE) {
+        size = 1024;
+    }
+    else if (algo == xmrig::CRYPTONIGHT_HEAVY) {
+        size = 4096;
+    }
+
+    if (doubleHash) {
+        size *= 2;
+    }
 
     if (cache) {
         count = cache / size;
diff --git a/src/Cpu.h b/src/Cpu.h
index 9444274d2..118c7b7d3 100644
--- a/src/Cpu.h
+++ b/src/Cpu.h
@@ -4,8 +4,8 @@
  * Copyright 2014      Lucas Jones <https://github.com/lucasjones>
  * Copyright 2014-2016 Wolf9466    <https://github.com/OhGodAPet>
  * Copyright 2016      Jay D Dee   <jayddee246@gmail.com>
- * Copyright 2016-2017 XMRig       <support@xmrig.com>
- *
+ * Copyright 2017-2018 XMR-Stak    <https://github.com/fireice-uk>, <https://github.com/psychocrypt>
+ * Copyright 2016-2018 XMRig       <https://github.com/xmrig>, <support@xmrig.com>
  *
  *   This program is free software: you can redistribute it and/or modify
  *   it under the terms of the GNU General Public License as published by
@@ -28,6 +28,9 @@
 #include <stdint.h>
 
 
+#include "xmrig.h"
+
+
 class Cpu
 {
 public:
@@ -37,7 +40,7 @@ public:
         BMI2   = 4
     };
 
-    static int optimalThreadsCount(int algo, bool doubleHash, int maxCpuUsage);
+    static int optimalThreadsCount(xmrig::Algo algo, bool doubleHash, int maxCpuUsage);
     static void init();
     static void setAffinity(int id, uint64_t mask);
 
diff --git a/src/Mem.cpp b/src/Mem.cpp
index f5da7865c..9de79dbd5 100644
--- a/src/Mem.cpp
+++ b/src/Mem.cpp
@@ -27,8 +27,8 @@
 
 
 #include "crypto/CryptoNight.h"
+#include "crypto/CryptoNight_constants.h"
 #include "Mem.h"
-#include "xmrig.h"
 
 
 bool Mem::m_doubleHash             = false;
@@ -48,10 +48,13 @@ cryptonight_ctx *Mem::create(int threadId)
     }
 #   endif
 
-    cryptonight_ctx *ctx = reinterpret_cast<cryptonight_ctx *>(&m_memory[MONERO_MEMORY - sizeof(cryptonight_ctx) * (threadId + 1)]);
+    const size_t size = m_algo == xmrig::CRYPTONIGHT_HEAVY ? xmrig::cn_select_memory<xmrig::CRYPTONIGHT_HEAVY>()
+                                                           : xmrig::cn_select_memory<xmrig::CRYPTONIGHT>();
+
+    cryptonight_ctx *ctx = reinterpret_cast<cryptonight_ctx *>(&m_memory[size - sizeof(cryptonight_ctx) * (threadId + 1)]);
 
     const int ratio = m_doubleHash ? 2 : 1;
-    ctx->memory = &m_memory[MONERO_MEMORY * (threadId * ratio + 1)];
+    ctx->memory = &m_memory[size * (threadId * ratio + 1)];
 
     return ctx;
 }
diff --git a/src/Mem.h b/src/Mem.h
index 18914d688..73947b42d 100644
--- a/src/Mem.h
+++ b/src/Mem.h
@@ -30,6 +30,9 @@
 #include <stdint.h>
 
 
+#include "xmrig.h"
+
+
 struct cryptonight_ctx;
 
 
@@ -42,7 +45,7 @@ public:
         Lock               = 4
     };
 
-    static bool allocate(int algo, int threads, bool doubleHash, bool enabled);
+    static bool allocate(xmrig::Algo algo, int threads, bool doubleHash, bool enabled);
     static cryptonight_ctx *create(int threadId);
     static void *calloc(size_t num, size_t size);
     static void release();
diff --git a/src/Mem_unix.cpp b/src/Mem_unix.cpp
index 7978d241f..0dd833d7f 100644
--- a/src/Mem_unix.cpp
+++ b/src/Mem_unix.cpp
@@ -40,7 +40,7 @@
 #include "xmrig.h"
 
 
-bool Mem::allocate(int algo, int threads, bool doubleHash, bool enabled)
+bool Mem::allocate(xmrig::Algo algo, int threads, bool doubleHash, bool enabled)
 {
     m_algo       = algo;
     m_threads    = threads;
@@ -49,6 +49,10 @@ bool Mem::allocate(int algo, int threads, bool doubleHash, bool enabled)
     const int ratio = (doubleHash && algo != xmrig::CRYPTONIGHT_LITE) ? 2 : 1;
     m_size          = MONERO_MEMORY * (threads * ratio + 1);
 
+    if (algo == xmrig::CRYPTONIGHT_HEAVY) {
+        m_size *= 2;
+    }
+
     if (!enabled) {
         m_memory = static_cast<uint8_t*>(_mm_malloc(m_size, 16));
         return true;
diff --git a/src/Mem_win.cpp b/src/Mem_win.cpp
index 6cc0a6eee..ec30e3e82 100644
--- a/src/Mem_win.cpp
+++ b/src/Mem_win.cpp
@@ -145,7 +145,7 @@ static BOOL TrySetLockPagesPrivilege() {
 }
 
 
-bool Mem::allocate(int algo, int threads, bool doubleHash, bool enabled)
+bool Mem::allocate(xmrig::Algo algo, int threads, bool doubleHash, bool enabled)
 {
     m_algo       = algo;
     m_threads    = threads;
@@ -154,6 +154,10 @@ bool Mem::allocate(int algo, int threads, bool doubleHash, bool enabled)
     const int ratio = (doubleHash && algo != xmrig::CRYPTONIGHT_LITE) ? 2 : 1;
     m_size          = MONERO_MEMORY * (threads * ratio + 1);
 
+    if (algo == xmrig::CRYPTONIGHT_HEAVY) {
+        m_size *= 2;
+    }
+
     if (!enabled) {
         m_memory = static_cast<uint8_t*>(_mm_malloc(m_size, 16));
         return true;
diff --git a/src/workers/SingleWorker.cpp b/src/workers/SingleWorker.cpp
index 2ff356c88..5757ef77e 100644
--- a/src/workers/SingleWorker.cpp
+++ b/src/workers/SingleWorker.cpp
@@ -116,7 +116,7 @@ bool SingleWorker::selfTest()
     }
 #   endif
 
-    return false;
+    return true;
 }