diff --git a/aegisub/FFmpegSource2/ffaudiosource.cpp b/aegisub/FFmpegSource2/ffaudiosource.cpp
index 1222924e1..f467280e9 100644
--- a/aegisub/FFmpegSource2/ffaudiosource.cpp
+++ b/aegisub/FFmpegSource2/ffaudiosource.cpp
@@ -150,7 +150,7 @@ Done:
 }
 
 int FFAudioSource::GetAudio(void *Buf, int64_t Start, int64_t Count, char *ErrorMsg, unsigned MsgSize) {
-	const size_t SizeConst = (av_get_bits_per_sample_format(CodecContext->sample_fmt) * CodecContext->channels) / 8;
+	const int64_t SizeConst = (av_get_bits_per_sample_format(CodecContext->sample_fmt) * CodecContext->channels) / 8;
 	size_t CurrentAudioBlock = FFMAX((int64_t)FindClosestAudioKeyFrame(Start) - 50, (int64_t)0);
 	memset(Buf, 0, SizeConst * Count);
 	AVPacket Packet;
@@ -306,7 +306,7 @@ MatroskaAudioSource::~MatroskaAudioSource() {
 }
 
 int MatroskaAudioSource::GetAudio(void *Buf, int64_t Start, int64_t Count, char *ErrorMsg, unsigned MsgSize) {
-	const size_t SizeConst = (av_get_bits_per_sample_format(CodecContext->sample_fmt) * CodecContext->channels) / 8;
+	const int64_t SizeConst = (av_get_bits_per_sample_format(CodecContext->sample_fmt) * CodecContext->channels) / 8;
 	size_t CurrentAudioBlock = FFMAX((int64_t)FindClosestAudioKeyFrame(Start) - 10, (int64_t)0);
 	avcodec_flush_buffers(CodecContext);
 
diff --git a/aegisub/FFmpegSource2/ffms.cpp b/aegisub/FFmpegSource2/ffms.cpp
index 6d20f4f83..213a20133 100644
--- a/aegisub/FFmpegSource2/ffms.cpp
+++ b/aegisub/FFmpegSource2/ffms.cpp
@@ -211,4 +211,4 @@ FFMS_API(int) FFMS_WriteIndex(const char *IndexFile, FrameIndex *TrackIndices, c
 
 FFMS_API(int) FFMS_GetPixFmt(const char *Name) {
 	return avcodec_get_pix_fmt(Name);
-}
\ No newline at end of file
+}
diff --git a/aegisub/FFmpegSource2/ffms2.html b/aegisub/FFmpegSource2/ffms2.html
index 24564b5e8..707d707cd 100644
--- a/aegisub/FFmpegSource2/ffms2.html
+++ b/aegisub/FFmpegSource2/ffms2.html
@@ -242,7 +242,7 @@ Note that --enable-w32threads is required for multithreaded decoding to work.
 <li>Fixed the accessing of codecprivate data with Haali's splitters</li>
 <li>Timecode output should be fixed to include decimals AND not be in scientific format</li>
 <li>Fixed a memory leak when using Haali's splitters</li>
-<li>Updated FFmpeg to rev X</li>
+<li>Updated FFmpeg to rev 18717</li>
 </ul></li>
 
 <li>2.00 beta 6<ul>