diff --git a/src/refresh-runtime.js b/src/refresh-runtime.js
index 80b962c..cbe001b 100644
--- a/src/refresh-runtime.js
+++ b/src/refresh-runtime.js
@@ -547,6 +547,12 @@ function isLikelyComponentType(type) {
  * Plugin utils
  */
 
+if (window.$RefreshReg$) {
+  throw new Error(
+    "React refresh runtime was loaded twice. Maybe you forgot the base path?",
+  );
+}
+
 export function getRefreshReg(filename) {
   return (type, id) => register(type, filename + " " + id);
 }