diff --git a/_extensions/diagram/diagram.lua b/_extensions/diagram/diagram.lua
index ea9e9ac..9d5a849 100644
--- a/_extensions/diagram/diagram.lua
+++ b/_extensions/diagram/diagram.lua
@@ -241,6 +241,8 @@ local function format_options (name)
   -- Prefer SVG for non-PDF output formats
   if pdf2svg then
     preferred_mime_types:insert(1, 'image/svg+xml')
+  else
+    preferred_mime_types:insert('image/svg+xml')
   end
   return {
     name = name,