I need to know how to replace a line after a pattern match with an empty line using SED

Hi How Are you?
I am doing fine!
I need to go now?
I will see you tomorrow!

Basically I need to replace the entire line containing "doing" with a blank line:
I need to the following output:

Hi How Are you?

I need to go now?
I will see you tomorrow!

Thanks in advance....

sed '/doing/s/.*//' file