diff --git a/include/maxscale/spinlock.h b/include/maxscale/spinlock.h
index 4c08ec108..c0d46356b 100644
--- a/include/maxscale/spinlock.h
+++ b/include/maxscale/spinlock.h
@@ -42,7 +42,7 @@ MXS_BEGIN_DECLS
  */
 typedef struct spinlock
 {
-    int lock;         /*< Is the lock held? */
+    volatile int lock;/*< Is the lock held? */
 #if SPINLOCK_PROFILE
     int spins;        /*< Number of spins on this lock */
     int maxspins;     /*< Max no of spins to acquire lock */