--- a/pthread_spin_trylock.c
+++ b/pthread_spin_trylock.c
@@ -61,7 +61,7 @@
   s = *lock;
 
   switch ((long)
-	  PTW32_INTERLOCKED_COMPARE_EXCHANGE_LONG ((PTW32_INTERLOCKED_PTR) &s->interlock,
+	  PTW32_INTERLOCKED_COMPARE_EXCHANGE_LONG ((PTW32_INTERLOCKED_LONGPTR) &s->interlock,
 					           (PTW32_INTERLOCKED_LONG) PTW32_SPIN_LOCKED,
 					           (PTW32_INTERLOCKED_LONG) PTW32_SPIN_UNLOCKED))
     {