React Native [runtime not ready]: TypeError: Cannot read property 'style' of undefined after upgrading from 0.73 to 0.78

Question

I'm working on a React Native project and recently upgraded it from version 0.73 to 0.78.

Upgrade Process I Followed:

I created a brand-new React Native 0.78 project using the CLI.
Verified that the new project runs correctly on a device/emulator.
Transferred all necessary files and folders from my existing 0.73 project (like src/, assets, fonts, etc.).
Reinstalled all required dependencies manually, matching the original project's package.json.

The Issue:

When I run the app on a real device, it builds and launches, but I get the following runtime error in the app (not in the console):

[runtime not ready]: TypeError: Cannot read property 'style' of undefined js engine: hermes

This happens as soon as the app loads. There are no errors shown in Metro or the terminal.

Please edit your question to include a minimal reproducible example so that readers can run your code to answer your question. The issue is currently not reproducible. — SNBS
– SNBS, Commented Apr 7 at 7:06
The best practice update the repo from 0.73 to 0.78 instead creating a brand new 0.78 repo — Fiido93
– Fiido93, Commented Apr 7 at 7:48
Same here after updating to RN 0.79.2 using the RN Upgrade helper and every recommended practice possible. Ran into some issues with the Bridging file and RNCPushNotificationIOS, but then after successfully fixing everything i get [runtime not ready]: TypeError: initialize is not a function (it is undefined), js engine: hermes — klevisx
– klevisx, Commented May 6 at 18:46
@klevisx Did you find the cause of your issue? Having the same with an upgrade to 0.80 and not finding anything — Ignacio Van Loy
– Ignacio Van Loy, Commented Jul 10 at 15:41

hrunk · Accepted Answer · 2025-04-28 10:49:18Z

1

In my case, this was because of ViewPropTypes. React Native removed ViewPropTypes in 0.74 (along with a bunch of other PropTypes).

You need to find out which library is responsible. The line number that caused the error was shown in the error message on the device, so I built the dev bundle:

npx react-native bundle --platform ios --dev true --bundle-output temp-bundle.js --entry-file src/main.tsx

(replace src/main.tsx with your entry file), looked at the relevant line in the temp-bundle.js file, and found that the issue was caused by react-native-snap-carousel (workaround here, using patch-package).

Afterwards I grep'd my entire node_modules folder to check for any more uses of ViewPropTypes.

answered Apr 28 at 10:49

hrunk

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