diff --git a/mjit.c b/mjit.c
index 58fe0cb1d1..efe281fb22 100644
--- a/mjit.c
+++ b/mjit.c
@@ -140,7 +140,7 @@ typedef intptr_t pid_t;
 #endif
 
 /* Atomically set function pointer if possible. */
-#define MJIT_ATOMIC_SET(var, val) ATOMIC_PTR_EXCHANGE(var, val)
+#define MJIT_ATOMIC_SET(var, val) (void)ATOMIC_PTR_EXCHANGE(var, val)
 
 /* A copy of MJIT portion of MRI options since MJIT initialization.  We
    need them as MJIT threads still can work when the most MRI data were