NSBackgroundColorAttributeName in textView doesn't respect range if highlighted word is first of a line

I'm implementing a "search in chat" feature and I want the searched word to be highlighted in messages. The problem, as described in title, is that if the word is the first of a line (long messages are clearly multi-line), the entire line is highlighted instead of the single word.

While debugging, I also tried to apply an underline instead of backgroundcolor, and the underline is correct. I can't figure out where's the problem. My app's chat is based on JSQMessagesViewController so I was thinking that the problem could be there.

[attributedString addAttribute:NSBackgroundColorAttributeName value:backColor] range:wordRange];
[attributedString addAttribute:NSUnderlineStyleAttributeName value:@(NSUnderlineStyleSingle)] range:wordRange];

cell.textView.attributedText = attributedString;

I don't post the code that calculates range because range is correct; in fact, if I look at attributedString's preview in debug (where I assign it to cell.textView.attributedText) I can see that only the word is highlighted, and not all the string.

Here's an example:

from NSBackgroundColorAttributeName in textView doesn't respect range if highlighted word is first of a line