diff --git a/aegisub/src/audio_provider_ffmpegsource.cpp b/aegisub/src/audio_provider_ffmpegsource.cpp
index 687388c09..8d474c621 100644
--- a/aegisub/src/audio_provider_ffmpegsource.cpp
+++ b/aegisub/src/audio_provider_ffmpegsource.cpp
@@ -143,6 +143,9 @@ void FFmpegSourceAudioProvider::LoadAudio(wxString filename) {
 		if (TrackNumber == FFMS_TRACKMASK_ALL)
 			TrackNumber = FFMS_GetFirstTrackOfType(Index, FFMS_TYPE_AUDIO, &ErrInfo);
 	}
+	else {
+		FFMS_CancelIndexing(Indexer);
+	}
 
 	// update access time of index file so it won't get cleaned away
 	if (!wxFileName(CacheName).Touch()) {
diff --git a/aegisub/src/video_provider_ffmpegsource.cpp b/aegisub/src/video_provider_ffmpegsource.cpp
index cddfdf79b..f131a773b 100644
--- a/aegisub/src/video_provider_ffmpegsource.cpp
+++ b/aegisub/src/video_provider_ffmpegsource.cpp
@@ -132,6 +132,9 @@ void FFmpegSourceVideoProvider::LoadVideo(wxString filename) {
 			TrackMask = FFMS_TRACKMASK_ALL;
 		Index = DoIndexing(Indexer, CacheName, TrackMask, GetErrorHandlingMode());
 	}
+	else {
+		FFMS_CancelIndexing(Indexer);
+	}
 
 	// update access time of index file so it won't get cleaned away
 	wxFileName(CacheName).Touch();