Spot the error

This Swift code contains one error – can you select the line that is incorrect?

Tip: You should mentally run the code from top to bottom, meaning that if line 3 says an integer should be returned and line 10 tries to return a string, line 10 is the wrong one.

function convertValue(height: Int) -> String {

    var result: String = "The height is "

    result += String(height)

    return result

}

print(convertValue(height: 14))