diff --git a/io/previewgenerator.cpp b/io/previewgenerator.cpp
index 2c89a851d..0bd8eaa38 100644
--- a/io/previewgenerator.cpp
+++ b/io/previewgenerator.cpp
@@ -217,6 +217,10 @@ void PreviewGenerator::finalize_media() {
 	}
 }
 
+void thumb_data_cleanup(void *info) {
+	delete [] static_cast<uint8_t*>(info);
+}
+
 void PreviewGenerator::generate_waveform() {
 	SwsContext* sws_ctx;
 	SwrContext* swr_ctx;
@@ -296,7 +300,7 @@ void PreviewGenerator::generate_waveform() {
 						linesize[0] = dstW*4;
 						sws_scale(sws_ctx, temp_frame->data, temp_frame->linesize, 0, temp_frame->height, &data, linesize);
 
-						s->video_preview = QImage(data, dstW, dstH, linesize[0], QImage::Format_RGBA8888);
+						s->video_preview = QImage(data, dstW, dstH, linesize[0], QImage::Format_RGBA8888, thumb_data_cleanup);
 						s->make_square_thumb();
 
 						// is video interlaced?