diff --git a/factoryWithTypeCheckers.js b/factoryWithTypeCheckers.js
index adbd752..99daccb 100644
--- a/factoryWithTypeCheckers.js
+++ b/factoryWithTypeCheckers.js
@@ -206,7 +206,8 @@ module.exports = function(isValidElement, throwOnDirectAccess) {
           }
         }
       }
-      if (props[propName] == null) {
+      // undefined == null and null == null are true
+      if (props[propName] === null || props[propName] === undefined) {
         if (isRequired) {
           if (props[propName] === null) {
             return new PropTypeError('The ' + location + ' `' + propFullName + '` is marked as required ' + ('in `' + componentName + '`, but its value is `null`.'));
diff --git a/package.json b/package.json
index 4440a03..b1c71ce 100644
--- a/package.json
+++ b/package.json
@@ -25,7 +25,6 @@
   },
   "homepage": "https://facebook.github.io/react/",
   "dependencies": {
-    "loose-envify": "^1.4.0",
     "object-assign": "^4.1.1",
     "react-is": "^16.8.1"
   },
@@ -47,6 +46,7 @@
     "eslint": "^5.13.0",
     "in-publish": "^2.0.0",
     "jest": "^19.0.2",
+    "loose-envify": "^1.4.0",
     "react": "^15.5.1",
     "uglifyify": "^3.0.4",
     "uglifyjs": "^2.4.10"
diff --git a/yarn.lock b/yarn.lock
index 366f1f5..b7d6128 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -2339,7 +2339,7 @@ loose-envify@^1.0.0, loose-envify@^1.1.0, loose-envify@^1.3.1:
 
 loose-envify@^1.4.0:
   version "1.4.0"
-  resolved "https://registry.yarnpkg.com/loose-envify/-/loose-envify-1.4.0.tgz#71ee51fa7be4caec1a63839f7e682d8132d30caf"
+  resolved "https://registry.npmjs.org/loose-envify/-/loose-envify-1.4.0.tgz#71ee51fa7be4caec1a63839f7e682d8132d30caf"
   integrity sha512-lyuxPGr/Wfhrlem2CL/UcnUc1zcqKAImBDzukY7Y5F/yQiNdko6+fRLevlw1HgMySw7f611UIY408EtxRSoK3Q==
   dependencies:
     js-tokens "^3.0.0 || ^4.0.0"