Qt release build requires debug DLLs

I have开发者_如何学编程 a rather weird problem deploying my application ... I compile the application in Release mode, but when I try to run it it requires QtCored4.dll (notice the letter d).

Why doesn't it require the non-debug dll, QtCore4.dll instead?

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I was including a debug 3rd party library build, rather than a release one ... Including the latter one fixed the errors.