diff --git a/words.spec b/words.spec
index 5c81fdf..21132c4 100644
--- a/words.spec
+++ b/words.spec
@@ -22,7 +22,7 @@ passwords.
 %build
 cd mwords
 dos2unix -o *; chmod a+r *
-cat [1-9]*.??? | egrep -v "'s$" | egrep  "^[[:alnum:]'&!,./-]+$" | sort --ignore-case --dictionary-order | uniq > moby
+cat [1-9]*.??? | egrep --invert-match "'s$" | egrep  "^[[:alnum:]'&!,./-]+$" | sort --ignore-case --dictionary-order | uniq > moby
 
 cat <<EOF >license.txt
 On June 1, 1996 Grady Ward announced that the fruits of