Curious problem with find/replace & regex

[JoeBloe]

calibre 2.6
Windows 8.1
In searching for a particular combination

find: (’)(\w{3,})
replace: \1 \2

it would find them quite handily, but when trying to replace it would give an error on some examples. When trying to replace

‘own ends’—what might those be?”

it would give error

calibre, version 2.6.0
ERROR: Cannot replace: Currently selected text does not match the search query. You must first click Find, before trying to replace

Now that I look back, it should not be finding that example at all, as an EM DASH is not a \w.(unless I am mistaken about this flavor of regex???)

[Phssthpok]

I just tested it for you -- an em dash is NOT a \w.