Swift hasSuffix method crashing app

I'm trying to detect whether or not a user's input ends with a blank space, and if it does, to remove that space. I'm using the .hasSuffix() method to see if the space exists, and it should return a boolean variable that I can test for and determine the proper course of action. However, when I check whether the value is true or false, the app crashes. Any thoughts on why that might be? Here's the code:

var guessEndsWithSpace: Bool = userGuess.hasSuffix(" ")

        // The above will return true if the string ends with a space, so when this happens, remove the space and then check their guess

        if (guessEndsWithSpace == true) {

            println("Guess ends with a space")

            // checkAnswer(userGuess)

        } else {

            println("Guess does not end with a space")
            // Otherwise, just check their guess

            // checkAnswer(userGuess)