diff --git a/cmThread.c b/cmThread.c
index 18c5f0b..fc4bf3f 100644
--- a/cmThread.c
+++ b/cmThread.c
@@ -1290,6 +1290,8 @@ bool     cmThFloatCAS( float*    addr, float    old, float    new )
 #endif
 }
 
+#define OS_VER_10_6
+
 bool     cmThPtrCAS(   void*    addr, void*    old, void*    neww )
 {
 #ifdef OS_OSX
@@ -1302,7 +1304,7 @@ bool     cmThPtrCAS(   void*    addr, void*    old, void*    neww )
     union 
     {
       void* addr;
-#ifdef OS_64
+#ifdef OS_VER_10_6
       int64_t   val;
 #else
       int val;
@@ -1314,7 +1316,7 @@ bool     cmThPtrCAS(   void*    addr, void*    old, void*    neww )
   
   ov.u.addr = old;
   nv.u.addr = neww;
-#ifdef OS_64
+#ifdef OS_VER_10_6
   int rv = OSAtomicCompareAndSwap64Barrier(ov.u.val,nv.u.val,(int64_t*)addr);
 #else
   int rv = OSAtomicCompareAndSwap32Barrier(ov.u.val,nv.u.val,(int*)addr);
@@ -1323,7 +1325,7 @@ bool     cmThPtrCAS(   void*    addr, void*    old, void*    neww )
 #endif
 
 #ifdef OS_LINUX
-#ifdef OS_64
+#ifdef OS_VER_10_6
   return  __sync_bool_compare_and_swap((long long*)addr, (long long)old, (long long)neww); 
 #else
   return  __sync_bool_compare_and_swap((int*)addr,(int)old,(int)neww);