diff --git a/src/generatedoc.c b/src/generatedoc.c
index e9240395..29c62c5e 100644
--- a/src/generatedoc.c
+++ b/src/generatedoc.c
@@ -428,6 +428,10 @@ static int Export_help(const char * path)
     fprintf(f, "  color-adjust: exact; /*Firefox*/\n");
     fprintf(f, " }\n");
     fprintf(f, "}\n");
+    fprintf(f, "@viewport {\n");
+    fprintf(f, "  width: device-width;\n");
+    fprintf(f, "  zoom: 1;\n");
+    fprintf(f, "}\n");
     fclose(f);
   }