diff --git a/io/media.cpp b/io/media.cpp
index d3080d911..4e0d17767 100644
--- a/io/media.cpp
+++ b/io/media.cpp
@@ -1,6 +1,7 @@
 #include "media.h"
 
 #include <QDebug>
+#include "io/previewgenerator.h"
 
 extern "C" {
 	#include <libavformat/avformat.h>
@@ -8,13 +9,17 @@ extern "C" {
 
 #include "project/clip.h"
 
-Media::Media() : ready(false) {}
+Media::Media() : ready(false), preview_gen(NULL) {}
 
 Media::~Media() {
     reset();
 }
 
 void Media::reset() {
+	if (preview_gen != NULL) {
+		preview_gen->cancel();
+		preview_gen->wait();
+	}
     for (int i=0;i<video_tracks.size();i++) {
         delete video_tracks.at(i);
     }
diff --git a/io/media.h b/io/media.h
index 678a1da55..41ec32e17 100644
--- a/io/media.h
+++ b/io/media.h
@@ -20,6 +20,7 @@
 
 struct Sequence;
 struct Clip;
+class PreviewGenerator;
 
 struct MediaStream {
 	int file_index;
@@ -50,6 +51,8 @@ struct Media {
     int save_id;
     bool ready;
 
+	PreviewGenerator* preview_gen;
+
     long get_length_in_frames(double frame_rate);
     MediaStream* get_stream_from_file_index(bool video, int index);
     void reset();
diff --git a/io/previewgenerator.cpp b/io/previewgenerator.cpp
index fe4eb0814..99e1e8d6c 100644
--- a/io/previewgenerator.cpp
+++ b/io/previewgenerator.cpp
@@ -26,9 +26,10 @@ PreviewGenerator::PreviewGenerator(QTreeWidgetItem* i, Media* m, bool r) :
 	media(m),
 	retrieve_duration(false),
 	contains_still_image(false),
-	replace(r)
+	replace(r),
+	cancelled(false)
 {
-    connect(this, SIGNAL(finished()), this, SLOT(deleteLater()));
+	connect(this, SIGNAL(finished()), this, SLOT(deleteLater()));
 }
 
 void PreviewGenerator::parse_media() {
@@ -227,12 +228,18 @@ void PreviewGenerator::generate_waveform() {
 							}
 							s->audio_preview.append(min >> 8);
 							s->audio_preview.append(max >> 8);
+							if (cancelled) break;
 						}
 					}
 
 					swr_free(&swr_ctx);
 					av_frame_unref(swr_frame);
 					av_frame_free(&swr_frame);
+
+					if (cancelled) {
+						end_of_file = true;
+						break;
+					}
 				}
 			}
 
@@ -314,4 +321,9 @@ void PreviewGenerator::run() {
         item->setToolTip(0, QString());
     }
     delete [] filename;
+	media->preview_gen = NULL;
+}
+
+void PreviewGenerator::cancel() {
+	cancelled = true;
 }
diff --git a/io/previewgenerator.h b/io/previewgenerator.h
index 15b1e805f..f0439a828 100644
--- a/io/previewgenerator.h
+++ b/io/previewgenerator.h
@@ -18,6 +18,7 @@ class PreviewGenerator : public QThread
 public:
 	PreviewGenerator(QTreeWidgetItem*, Media*, bool);
     void run();
+	void cancel();
 signals:
 	void set_icon(int, bool);
 private:
@@ -30,6 +31,7 @@ private:
 	bool retrieve_duration;
 	bool contains_still_image;
 	bool replace;
+	bool cancelled;
 };
 
 #endif // PREVIEWGENERATOR_H
diff --git a/panels/project.cpp b/panels/project.cpp
index 3def46d78..a2877a62c 100644
--- a/panels/project.cpp
+++ b/panels/project.cpp
@@ -163,8 +163,8 @@ void Project::start_preview_generator(QTreeWidgetItem* item, Media* media, bool
     MediaThrobber* throbber = new MediaThrobber(item);
 
 	PreviewGenerator* pg = new PreviewGenerator(item, media, replacing);
+	media->preview_gen = pg;
 	connect(pg, SIGNAL(set_icon(int, bool)), throbber, SLOT(stop(int, bool)));
-    connect(pg, SIGNAL(finished()), pg, SLOT(deleteLater()));
     pg->start(QThread::LowPriority);
 }
 
@@ -1209,7 +1209,7 @@ void Project::save_recent_projects() {
 
 void Project::clear_recent_projects() {
     recent_projects.clear();
-    save_recent_projects();
+	save_recent_projects();
 }
 
 void Project::add_recent_project(QString url) {
diff --git a/panels/project.h b/panels/project.h
index d52c089bd..efb2129ac 100644
--- a/panels/project.h
+++ b/panels/project.h
@@ -93,7 +93,7 @@ private:
 	QString get_file_name_from_path(const QString &path);
 private slots:
     void rename_media(QTreeWidgetItem* item, int column);
-    void clear_recent_projects();
+	void clear_recent_projects();
 };
 
 class MediaThrobber : public QObject {