diff --git a/aegisub/FFmpegSource2/ffaudiosource.cpp b/aegisub/FFmpegSource2/ffaudiosource.cpp
index 0c3892476..aa71a7c61 100644
--- a/aegisub/FFmpegSource2/ffaudiosource.cpp
+++ b/aegisub/FFmpegSource2/ffaudiosource.cpp
@@ -453,7 +453,9 @@ int FFMatroskaAudio::DecodeNextAudioBlock(int64_t *Count, int AudioBlock, char *
 	TempPacket.data = MC.Buffer;
 	TempPacket.size = FrameSize;
 	if (Frames[AudioBlock].KeyFrame)
-		TempPacket.flags = PKT_FLAG_KEY;
+		TempPacket.flags = AV_PKT_FLAG_KEY;
+	else
+		TempPacket.flags = 0;
 
 	while (TempPacket.size > 0) {
 		int TempOutputBufSize = AVCODEC_MAX_AUDIO_FRAME_SIZE;
@@ -510,7 +512,7 @@ int FFHaaliAudio::DecodeNextAudioBlock(int64_t *AFirstStartTime, int64_t *Count,
 			Packet.data = Data;
 			Packet.size = pMMF->GetActualDataLength();
 			if (pMMF->IsSyncPoint() == S_OK)
-				Packet.flags = PKT_FLAG_KEY;
+				Packet.flags = AV_PKT_FLAG_KEY;
 			else
 				Packet.flags = 0;
 
diff --git a/aegisub/FFmpegSource2/ffvideosource.cpp b/aegisub/FFmpegSource2/ffvideosource.cpp
index adb0319d3..bbe8cb881 100644
--- a/aegisub/FFmpegSource2/ffvideosource.cpp
+++ b/aegisub/FFmpegSource2/ffvideosource.cpp
@@ -528,9 +528,10 @@ int FFMatroskaVideo::DecodeNextFrame(int64_t *AFirstStartTime, char *ErrorMsg, u
 		Packet.data = MC.Buffer;
 		Packet.size = FrameSize;
 		if (FrameFlags & FRAME_KF)
-			Packet.flags = PKT_FLAG_KEY;
+			Packet.flags = AV_PKT_FLAG_KEY;
 		else
 			Packet.flags = 0;
+
 		avcodec_decode_video2(CodecContext, DecodeFrame, &FrameFinished, &Packet);
 
 		if (FrameFinished)
@@ -768,7 +769,7 @@ int FFHaaliVideo::DecodeNextFrame(int64_t *AFirstStartTime, char *ErrorMsg, unsi
 			Packet.data = Data;
 			Packet.size = pMMF->GetActualDataLength();
 			if (pMMF->IsSyncPoint() == S_OK)
-				Packet.flags = PKT_FLAG_KEY;
+				Packet.flags = AV_PKT_FLAG_KEY;
 			else
 				Packet.flags = 0;
 
diff --git a/aegisub/FFmpegSource2/indexing.cpp b/aegisub/FFmpegSource2/indexing.cpp
index 6d3f668d7..5cd1696a9 100644
--- a/aegisub/FFmpegSource2/indexing.cpp
+++ b/aegisub/FFmpegSource2/indexing.cpp
@@ -311,6 +311,10 @@ FFIndex *FFHaaliIndexer::DoIndexing(char *ErrorMsg, unsigned MsgSize) {
 			AVCodecContext *AudioCodecContext = AudioContexts[Track].CTX;
 			pMMF->GetPointer(&TempPacket.data);
 			TempPacket.size = pMMF->GetActualDataLength();
+			if (pMMF->IsSyncPoint() == S_OK)
+				TempPacket.flags = AV_PKT_FLAG_KEY;
+			else
+				TempPacket.flags = 0;
 
 			while (TempPacket.size > 0) {
 				int dbsize = AVCODEC_MAX_AUDIO_FRAME_SIZE*10;
@@ -453,7 +457,9 @@ FFIndex *FFMatroskaIndexer::DoIndexing(char *ErrorMsg, unsigned MsgSize) {
 			TempPacket.data = MC.Buffer;
 			TempPacket.size = FrameSize;
 			if ((FrameFlags & FRAME_KF) != 0)
-				TempPacket.flags = PKT_FLAG_KEY;
+				TempPacket.flags = AV_PKT_FLAG_KEY;
+			else
+				TempPacket.flags = 0;
 
 			while (TempPacket.size > 0) {
 				int dbsize = AVCODEC_MAX_AUDIO_FRAME_SIZE*10;
@@ -594,9 +600,9 @@ FFIndex *FFLAVFIndexer::DoIndexing(char *ErrorMsg, unsigned MsgSize) {
 
 		// Only create index entries for video for now to save space
 		if (FormatContext->streams[Packet.stream_index]->codec->codec_type == CODEC_TYPE_VIDEO) {
-			(*TrackIndices)[Packet.stream_index].push_back(TFrameInfo(Packet.dts, (Packet.flags & PKT_FLAG_KEY) ? 1 : 0));
+			(*TrackIndices)[Packet.stream_index].push_back(TFrameInfo(Packet.dts, (Packet.flags & AV_PKT_FLAG_KEY) ? 1 : 0));
 		} else if (FormatContext->streams[Packet.stream_index]->codec->codec_type == CODEC_TYPE_AUDIO && (IndexMask & (1 << Packet.stream_index))) {
-			(*TrackIndices)[Packet.stream_index].push_back(TFrameInfo(Packet.dts, AudioContexts[Packet.stream_index].CurrentSample, (Packet.flags & PKT_FLAG_KEY) ? 1 : 0));
+			(*TrackIndices)[Packet.stream_index].push_back(TFrameInfo(Packet.dts, AudioContexts[Packet.stream_index].CurrentSample, (Packet.flags & AV_PKT_FLAG_KEY) ? 1 : 0));
 			AVCodecContext *AudioCodecContext = FormatContext->streams[Packet.stream_index]->codec;
 			TempPacket.data = Packet.data;
 			TempPacket.size = Packet.size;