diff --git a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
index ea789376de0f..45de21c210c1 100644
--- a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
+++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
@@ -1795,6 +1795,7 @@ vchiq_compat_ioctl_await_completion(struct file *file,
 	struct vchiq_await_completion32 args32;
 	struct vchiq_completion_data32 completion32;
 	unsigned int *msgbufcount32;
+	unsigned int msgbufcount_native;
 	compat_uptr_t msgbuf32;
 	void *msgbuf;
 	void **msgbufptr;
@@ -1906,7 +1907,11 @@ vchiq_compat_ioctl_await_completion(struct file *file,
 			 sizeof(completion32)))
 		return -EFAULT;
 
-	args32.msgbufcount--;
+	if (get_user(msgbufcount_native, &args->msgbufcount))
+		return -EFAULT;
+
+	if (!msgbufcount_native)
+		args32.msgbufcount--;
 
 	msgbufcount32 =
 		&((struct vchiq_await_completion32 __user *)arg)->msgbufcount;