diff --git a/include/FFmpegUtilities.h b/include/FFmpegUtilities.h
index 7daf0bc5..c637f944 100644
--- a/include/FFmpegUtilities.h
+++ b/include/FFmpegUtilities.h
@@ -122,6 +122,9 @@
 	#ifndef PIX_FMT_YUV420P
 		#define PIX_FMT_YUV420P AV_PIX_FMT_YUV420P
 	#endif
+	#ifndef PIX_FMT_YUV444P
+		#define PIX_FMT_YUV444P AV_PIX_FMT_YUV444P
+	#endif
 
 	// FFmpeg's libavutil/common.h defines an RSHIFT incompatible with Ruby's
 	// definition in ruby/config.h, so we move it to FF_RSHIFT
diff --git a/src/FFmpegWriter.cpp b/src/FFmpegWriter.cpp
index 5797d09e..1fd19b43 100644
--- a/src/FFmpegWriter.cpp
+++ b/src/FFmpegWriter.cpp
@@ -438,6 +438,7 @@ void FFmpegWriter::SetOption(StreamType stream, std::string name, std::string va
 						av_opt_set_int(c->priv_data, "qp", std::min(std::stoi(value), 51), 0); // 0-51
 						if (std::stoi(value) == 0) {
 							av_opt_set(c->priv_data, "preset", "veryslow", 0);
+							c->pix_fmt = PIX_FMT_YUV444P; // no chroma subsampling
 						}
 						break;
 					case AV_CODEC_ID_HEVC :
@@ -498,6 +499,7 @@ void FFmpegWriter::SetOption(StreamType stream, std::string name, std::string va
 						av_opt_set_int(c->priv_data, "crf", std::min(std::stoi(value), 51), 0); // 0-51
 						if (std::stoi(value) == 0) {
 							av_opt_set(c->priv_data, "preset", "veryslow", 0);
+							c->pix_fmt = PIX_FMT_YUV444P; // no chroma subsampling
 						}
 						break;
 					case AV_CODEC_ID_HEVC :