rails 3.2 development mode is not displaying the full error page with backtrace etc

Question

I just upgraded to rails 3.2 Everything is working fine except error pages no longer show the normal development debug info. Instead it's showing the standard production error page (white background with red text in the middle:

"We're sorry, but something went wrong. We've been notified about this issue and we'll take a look at it shortly."

Is there a new setting or something I'm missing for rails 3.2? I've read over the upgrade instructions and do not see it mentioned anywhere. I tried downgrading to 3.1.3 and the error pages work again so this is definitely a rails 3.2 issue. Thanks.