I guess it may be something to do with this Preact commit: https://github.com/developit/preact/commit/a5b286b0affa2282f70e9834a05095a15a00166b With Preact 5.6.0: http://jsfiddle.net/28ckgyzj/3/ With Preact 5.2.0-beta.0: http://jsfiddle.net/5tzxLy7d/2/