Cocoa error 2048 when using NSRegularExpression in Cocoa

I'm building a regular expression for use in a parser in an iOS app. Here's my code:

NSRegularExpression *regex =
[NSRegularExpression regularExpressionWithPattern:@"(?<=#EXT[^\r\n]*[\r\n]+)[^#][^\r\n]+"
                                          options:NSRegularExpressionAnchorsMatchLines
                                            error:&regexError
 ];
if (regexError) {
    NSLog(@"regexError: %@", regexError);
    return nil;
}

From this answer.

This gives out this error:

regexError: Error Domain=NSCocoaErrorDomain Code=2048 "The operation couldn’t be completed. (Cocoa error 2048.)" UserInfo=0x8e86670 {NSInvalidValue=(?<=#EXT[^

Cocoa error 2048 is an NSFormattingErrorMinimum according to the docs... But there's literally no further explanation.

What does it mean?