diff --git a/gui/pdfworker.cpp b/gui/pdfworker.cpp
index e7a4bfb..c792fe5 100644
--- a/gui/pdfworker.cpp
+++ b/gui/pdfworker.cpp
@@ -67,11 +67,11 @@ struct Renderer
 	}
 };
 
-QFuture<PdfPreview> PdfWorker::generatePreviews(QVector<SearchResult> paths, double scalefactor)
+QFuture<PdfPreview> PdfWorker::generatePreviews(const QVector<SearchResult> paths, double scalefactor)
 {
 	QVector<PdfPreview> previews;
 
-	for(SearchResult &sr : paths)
+	for(const SearchResult &sr : paths)
 	{
 		for(int page : sr.pages)
 		{
diff --git a/gui/pdfworker.h b/gui/pdfworker.h
index bf59072..efb5900 100644
--- a/gui/pdfworker.h
+++ b/gui/pdfworker.h
@@ -16,7 +16,7 @@ class PdfWorker : public QObject
 {
 	Q_OBJECT
   public:
-	QFuture<PdfPreview> generatePreviews(QVector<SearchResult> paths, double scalefactor);
+	QFuture<PdfPreview> generatePreviews(const QVector<SearchResult> paths, double scalefactor);
 };
 
 #endif // PDFWORKER_H