Not at all! This is an issue that happens when you do not write a sed command properly. This is common with substitution commands where you are trying to either match or replace a string with spaces.
For example, running the following command will result in an "unterminated" error: sed s/hello/welcome back/g hello.txt.
You can fix this by adding the "\\" escape character before your spaces. This is a special character that tells sed to include the space when either searching or replacing text.
With that, the correct version of the command above looks something like this: sed s/hello/welcome\\ back/g hello.txt.