diff --git a/src/Cpu.h b/src/Cpu.h
index 292c6c6c3..7f1f76141 100644
--- a/src/Cpu.h
+++ b/src/Cpu.h
@@ -25,6 +25,9 @@
 #define __CPU_H__
 
 
+#include <stdint.h>
+
+
 class Cpu
 {
 public:
@@ -36,7 +39,7 @@ public:
 
     static int optimalThreadsCount(int algo, bool doubleHash, int maxCpuUsage);
     static void init();
-    static void setAffinity(int id, unsigned long mask);
+    static void setAffinity(int id, uint64_t mask);
 
     static inline bool hasAES()       { return m_flags & AES; }
     static inline bool isX64()        { return m_flags & X86_64; }
diff --git a/src/Cpu_unix.cpp b/src/Cpu_unix.cpp
index 1b7c6b0a8..925e0c0a0 100644
--- a/src/Cpu_unix.cpp
+++ b/src/Cpu_unix.cpp
@@ -40,7 +40,7 @@ void Cpu::init()
 }
 
 
-void Cpu::setAffinity(int id, unsigned long mask)
+void Cpu::setAffinity(int id, uint64_t mask)
 {
     cpu_set_t set;
     CPU_ZERO(&set);
diff --git a/src/Cpu_win.cpp b/src/Cpu_win.cpp
index fe4ea0ba4..13113a178 100644
--- a/src/Cpu_win.cpp
+++ b/src/Cpu_win.cpp
@@ -41,7 +41,7 @@ void Cpu::init()
 }
 
 
-void Cpu::setAffinity(int id, unsigned long mask)
+void Cpu::setAffinity(int id, uint64_t mask)
 {
     if (id == -1) {
         SetProcessAffinityMask(GetCurrentProcess(), mask);