diff --git a/src/h265.c b/src/h265.c
index dd5104e..81daeae 100644
--- a/src/h265.c
+++ b/src/h265.c
@@ -635,11 +635,21 @@ int h265_set_controls(struct request_data *driver_data,
 		.ptr = &scaling_matrix,
 		.size = sizeof(scaling_matrix),
 	};
+	/*
+	 * iter18 α-22 TEST: skip DECODE_PARAMS submission.
+	 * error_idx=4 from S_EXT_CTRLS showed DECODE_PARAMS fails validation.
+	 * If removing it from the batch lets SPS/PPS/SLICE/SCALING_MATRIX
+	 * stage correctly, the bug is isolated to DECODE_PARAMS validation.
+	 */
+#if 0
 	controls[n++] = (struct v4l2_ext_control){
 		.id = V4L2_CID_STATELESS_HEVC_DECODE_PARAMS,
 		.ptr = &decode_params,
 		.size = sizeof(decode_params),
 	};
+#else
+	(void)decode_params;
+#endif
 
 	rc = v4l2_set_controls(driver_data->video_fd,
 			       surface_object->request_fd,