diff --git a/Libraries/Core/ReactNativeVersionCheck.js b/Libraries/Core/ReactNativeVersionCheck.js
index 47dda1f6895..6b4c0973e57 100644
--- a/Libraries/Core/ReactNativeVersionCheck.js
+++ b/Libraries/Core/ReactNativeVersionCheck.js
@@ -41,6 +41,7 @@ exports.checkVersions = function checkVersions(): void {
 function _formatVersion(
   version:
     | {major: number, minor: number, patch: number, prerelease: ?number}
+    | {major: number, minor: number, patch: number, prerelease: ?string}
     | $TEMPORARY$object<{
         major: number,
         minor: number,