diff --git a/src/Cpu_mac.cpp b/src/Cpu_mac.cpp
index 3b6c4400..357e15ef 100644
--- a/src/Cpu_mac.cpp
+++ b/src/Cpu_mac.cpp
@@ -40,6 +40,6 @@ void Cpu::init()
 }
 
 
-void Cpu::setAffinity(int id, unsigned long mask)
+void Cpu::setAffinity(int id, uint64_t mask)
 {
 }