diff --git a/.proxyrc.js b/.proxyrc.js
new file mode 100644
index 00000000..b6a52a81
--- /dev/null
+++ b/.proxyrc.js
@@ -0,0 +1,15 @@
+module.exports = function(app) {
+  // `app` is an Express instance
+  app.use(function(req, res, next) {
+    const sh = res.setHeader;
+    res.setHeader = function(key, value) {
+      // remove pointless/incorrect charset from binary responses:
+      if (/^content-type$/i.test(key)) {
+        const m = value && value.match(/^(image\/|application\/wasm); charset=.+$/);
+        if (m) value = m[1];
+      }
+      return sh.call(this, key, value);
+    }
+    next();
+  });
+};