diff --git a/src/calibre/ebooks/pdf/render/from_html.py b/src/calibre/ebooks/pdf/render/from_html.py
index ea68ca89b1..191da98893 100644
--- a/src/calibre/ebooks/pdf/render/from_html.py
+++ b/src/calibre/ebooks/pdf/render/from_html.py
@@ -184,7 +184,8 @@ class PDFWriter(QObject):
             self.painter.restore()
 
         QTimer.singleShot(0, self.render_book)
-        self.loop.exec_()
+        if self.loop.exec_() == 1:
+            raise Exception('PDF Output failed, see log for details')
 
         if self.toc is not None and len(self.toc) > 0:
             self.doc.add_outline(self.toc)