diff --git a/src/context.c b/src/context.c
index c05caf2..705c742 100644
--- a/src/context.c
+++ b/src/context.c
@@ -270,6 +270,14 @@ VAStatus RequestCreateContext(VADriverContextP context, VAConfigID config_id,
 				(picture_height + 15) / 16 - 1;
 			dummy_sps.profile_idc = 100; /* High */
 			dummy_sps.level_idc = 41;
+			/*
+			 * FRAME_MBS_ONLY required: rkvdec_h264_validate_sps
+			 * doubles height for non-frame-mbs-only streams to
+			 * compute frame-height from field-height. Without
+			 * this flag, dummy with (height_in_map_units+1)*16
+			 * = 1088 doubles to 2176 > coded_fmt 1080 → -EINVAL.
+			 */
+			dummy_sps.flags = V4L2_H264_SPS_FLAG_FRAME_MBS_ONLY;
 
 			dummy_ctrl.id = V4L2_CID_STATELESS_H264_SPS;
 			dummy_ctrl.ptr = &dummy_sps;