diff --git a/src/HTMLRenderer/install.cc b/src/HTMLRenderer/install.cc
index 2421bce..486751f 100644
--- a/src/HTMLRenderer/install.cc
+++ b/src/HTMLRenderer/install.cc
@@ -194,7 +194,7 @@ void HTMLRenderer::install_embedded_font(GfxFont * font, const string & suffix,
if(system((boost::format("fontforge -script %1% 2>%2%") % script_path % (tmp_dir / NULL_FILENAME)).str().c_str()) != 0)
cerr << "Warning: fontforge failed." << endl;
- add_tmp_file("null");
+ add_tmp_file(NULL_FILENAME);
export_remote_font(fn_id, ".ttf", "truetype", font);
}