Software :: Using Sed To Search And Replace Does Not Accept Spaces?

Back to the problem: I wrote a little bash script that people around here can run to search and replace strings in the current directory and all subdirectories. However, whenever there is a space in the new string (the one doing the replacing), I get this error:

Sed: -e expression #1, char 9: unterminated `s' command

My code looks like this:

Code:
find ./ -type f -not -name find_SNR.sh -exec sed -i 's/'$FIND_SNR_STR1/$FIND_SNR_STR2/'' {} ;