diff --git a/include/media/v4l2-ioctl.h b/include/media/v4l2-ioctl.h
index d4c7729..fbeb00e 100644
--- a/include/media/v4l2-ioctl.h
+++ b/include/media/v4l2-ioctl.h
@@ -179,7 +179,7 @@
 	int (*vidioc_g_modulator)      (struct file *file, void *fh,
 					struct v4l2_modulator *a);
 	int (*vidioc_s_modulator)      (struct file *file, void *fh,
-					struct v4l2_modulator *a);
+					const struct v4l2_modulator *a);
 	/* Crop ioctls */
 	int (*vidioc_cropcap)          (struct file *file, void *fh,
 					struct v4l2_cropcap *a);