diff --git a/src/HTMLRenderer/export.cc b/src/HTMLRenderer/export.cc
index 00fbcab..ed7af33 100644
--- a/src/HTMLRenderer/export.cc
+++ b/src/HTMLRenderer/export.cc
@@ -18,14 +18,14 @@ void HTMLRenderer::export_remote_font(const FontInfo & info, const string & suff
     allcss_fout << "@font-face{font-family:f" << info.id << ";src:url(";
 
     {
-        const char * fn = str_fmt("f%llx%s", info.id, suffix.c_str());
+        auto fn = str_fmt("f%llx%s", info.id, suffix.c_str());
         if(param->single_html)
         {
-            allcss_fout << "'data:font/" << fontfileformat << ";base64," << base64stream(ifstream(tmp_dir + "/" + fn, ifstream::binary)) << "'";
+            allcss_fout << "'data:font/" << fontfileformat << ";base64," << base64stream(ifstream(tmp_dir + "/" + (char*)fn, ifstream::binary)) << "'";
         }
         else
         {
-            allcss_fout << fn;
+            allcss_fout << (char*)fn;
         }
     }