diff --git a/src/amd/vulkan/radv_video_enc.c b/src/amd/vulkan/radv_video_enc.c
index 74ce86443d4..e9781fbbaed 100644
--- a/src/amd/vulkan/radv_video_enc.c
+++ b/src/amd/vulkan/radv_video_enc.c
@@ -3163,6 +3163,15 @@ radv_video_patch_encode_session_parameters(struct radv_device *device, struct vk
       }
       break;
    case VK_VIDEO_CODEC_OPERATION_ENCODE_H265_BIT_KHR: {
+      for (unsigned i = 0; i < params->h265_enc.h265_sps_count; i++) {
+         /* VCN supports only the following block sizes (resulting in 64x64 CTBs with any coding
+          * block size) */
+         params->h265_enc.h265_sps[i].base.log2_min_luma_coding_block_size_minus3 = 0;
+         params->h265_enc.h265_sps[i].base.log2_diff_max_min_luma_coding_block_size = 3;
+         params->h265_enc.h265_sps[i].base.log2_min_luma_transform_block_size_minus2 = 0;
+         params->h265_enc.h265_sps[i].base.log2_diff_max_min_luma_transform_block_size = 3;
+      }
+
       for (unsigned i = 0; i < params->h265_enc.h265_pps_count; i++) {
          /* cu_qp_delta needs to be enabled if rate control is enabled. VCN2 and newer can also enable
           * it with rate control disabled. Since we don't know what rate control will be used, we