diff --git a/gui/pdfworker.cpp b/gui/pdfworker.cpp
index ad9490a..d4a683f 100644
--- a/gui/pdfworker.cpp
+++ b/gui/pdfworker.cpp
@@ -46,6 +46,7 @@ struct Renderer
 		result->setRenderHint(Poppler::Document::TextAntialiasing);
 		QMutexLocker locker(&cacheMutex);
 		documentcache.insert(path, result);
+		locker.unlock();
 		return result;
 	}