While integrating Chartboost into MoPub for an iOS app, I encountered a crash every time there is a Chartboost ad loading.

The error is:

ChartboostInterstitialCustomEvent requestAdWithSize customEventInfo unrecognized selector 

I thought it is a bug with MoPub at first (my experience tells me as MMedia crashes at times too).

After researching a while, I found out the crash is because MoPub tried to load a banner ad, while Chartboost does not have banner ads! Chartboost ONLY has interstitial ads!

To solve, you have to disable banner ads in MoPub portal for Chartboost..