Title: Uncaught ReferenceError Last modified: January 25, 2020 --- # Uncaught ReferenceError * Resolved [eitanc](https://wordpress.org/support/users/eitanc/) * (@eitanc) * [6 years, 3 months ago](https://wordpress.org/support/topic/uncaught-referenceerror-21/) * Hi, I use the plugin’s latest version with the latest WP and latest Chrome. Chrome gives the following error that looks related to your plugin: ” VM2718: 2 Uncaught ReferenceError: lazySizes is not defined at :2:1 at t.activateScript( rocket-loader.min.js:1) at rocket-loader.min.js:1 at t.run (rocket-loader.min. js:1) at rocket-loader.min.js:1 at rocket-loader.min.js:1 (anonymous) @ VM2718: 2 t.activateScript @ rocket-loader.min.js:1 (anonymous) @ rocket-loader.min.js: 1 t.run @ rocket-loader.min.js:1 (anonymous) @ rocket-loader.min.js:1 (anonymous) @ rocket-loader.min.js:1 load (async) t.runOnLoad @ rocket-loader.min.js:1 x @ rocket-loader.min.js:1 (anonymous) @ rocket-loader.min.js:1 (anonymous) @ rocket- loader.min.js:1 (anonymous) @ rocket-loader.min.js:1 ” * Can you look into this? * The page I need help with: _[[log in](https://login.wordpress.org/?redirect_to=https%3A%2F%2Fwordpress.org%2Fsupport%2Ftopic%2Funcaught-referenceerror-21%2F%3Foutput_format%3Dmd&locale=en_US) to see the link]_ Viewing 2 replies - 1 through 2 (of 2 total) * Plugin Support [Dimitris – WPMU DEV Support](https://wordpress.org/support/users/wpmudev-support6/) * (@wpmudev-support6) * [6 years, 3 months ago](https://wordpress.org/support/topic/uncaught-referenceerror-21/#post-12366191) * Hello there [@eitanc](https://wordpress.org/support/users/eitanc/) * This seems like a Smush Lazy Loading issue, is this correct? You can temporarily disable that option to confirm that. * If so, could you please open a ticket in Smush forums? [https://wordpress.org/support/plugin/wp-smushit#new-post](https://wordpress.org/support/plugin/wp-smushit#new-post) * Thank you, Dimitris * Thread Starter [eitanc](https://wordpress.org/support/users/eitanc/) * (@eitanc) * [6 years, 3 months ago](https://wordpress.org/support/topic/uncaught-referenceerror-21/#post-12366615) * Nevermind, I fixed it. my bad – the plugin of Hummingbird, I tweaked it too hard… 😉 Thanks! Viewing 2 replies - 1 through 2 (of 2 total) The topic ‘Uncaught ReferenceError’ is closed to new replies. * ![](https://ps.w.org/hummingbird-performance/assets/icon-256x256.gif?rev=2633221) * [Hummingbird Performance - Cache & Page Speed Optimization for Core Web Vitals | Critical CSS | Minify CSS | Defer CSS Javascript | CDN](https://wordpress.org/plugins/hummingbird-performance/) * [Frequently Asked Questions](https://wordpress.org/plugins/hummingbird-performance/#faq) * [Support Threads](https://wordpress.org/support/plugin/hummingbird-performance/) * [Active Topics](https://wordpress.org/support/plugin/hummingbird-performance/active/) * [Unresolved Topics](https://wordpress.org/support/plugin/hummingbird-performance/unresolved/) * [Reviews](https://wordpress.org/support/plugin/hummingbird-performance/reviews/) * 2 replies * 2 participants * Last reply from: [eitanc](https://wordpress.org/support/users/eitanc/) * Last activity: [6 years, 3 months ago](https://wordpress.org/support/topic/uncaught-referenceerror-21/#post-12366615) * Status: resolved