diff --git a/platforms/nuttx/src/px4/common/hrt_ioctl.c b/platforms/nuttx/src/px4/common/hrt_ioctl.c
index 4cba925a47a0..4c0a7d6aab26 100644
--- a/platforms/nuttx/src/px4/common/hrt_ioctl.c
+++ b/platforms/nuttx/src/px4/common/hrt_ioctl.c
@@ -354,7 +354,7 @@ hrt_ioctl(unsigned int cmd, unsigned long arg)
 #ifdef PX4_USERSPACE_HRT
 			*(uintptr_t *)arg = hrt_absolute_time_usr_base();
 #else
-			*(uintptr_t *)arg = NULL;
+			*(uintptr_t *)arg = (uintptr_t)NULL;
 #endif
 		}
 		break;