package.json

@@ -1,6 +1,6 @@
 {
   "name": "mobx-react",
-  "version": "5.4.1",
+  "version": "5.4.2",
   "description": "React bindings for MobX. Create fully reactive components.",
   "main": "index.js",
   "jsnext:main": "index.module.js",
@@ -73,7 +73,6 @@
   },
   "dependencies": {
     "hoist-non-react-statics": "^3.0.0",
-    "react-is": "^16.3.2",
     "react-lifecycles-compat": "^3.0.2"
   },
   "keywords": [

src/observer.js

@@ -1,8 +1,5 @@
-import React, { Component, PureComponent } from "react"
+import React, { Component, PureComponent, forwardRef } from "react"
 import hoistStatics from "hoist-non-react-statics"
-// FIXME: This fails in rollup, sadly, as a full import is bigger :-(
-// import { ForwardRef }  from "react-is"
-import * as ReactIs from "react-is"
 import { createAtom, Reaction, _allowStateChanges, $mobx } from "mobx"
 import { findDOMNode as baseFindDOMNode } from "react-dom"
 
@@ -29,6 +26,10 @@ export const renderReporter = new EventEmitter()
 const skipRenderKey = newSymbol("skipRender")
 const isForcingUpdateKey = newSymbol("isForcingUpdate")
 
+// Using react-is had some issues (and operates on elements, not on types), see #608 / #609
+const ReactForwardRefSymbol =
+    typeof forwardRef === "function" && forwardRef((_props, _ref) => {})["$$typeof"]
+
 /**
  * Helper to set `prop` to `this` as non-enumerable (hidden prop)
  * @param target
@@ -325,7 +326,7 @@ export function observer(arg1, arg2) {
     // Unwrap forward refs into `<Observer>` component
     // we need to unwrap the render, because it is the inner render that needs to be tracked,
     // not the ForwardRef HoC
-    if (componentClass["$$typeof"] === ReactIs.ForwardRef) {
+    if (ReactForwardRefSymbol && componentClass["$$typeof"] === ReactForwardRefSymbol) {
         const baseRender = componentClass.render
         if (typeof baseRender !== "function")
             throw new Error("render property of ForwardRef was not a function")