diff --git a/book/01-introduction/sections/about-version-control.asc b/book/01-introduction/sections/about-version-control.asc
index a29ed2f56..067b142e5 100644
--- a/book/01-introduction/sections/about-version-control.asc
+++ b/book/01-introduction/sections/about-version-control.asc
@@ -22,7 +22,7 @@ To deal with this issue, programmers long ago developed local VCSs that had a si
 .Local version control.
 image::images/local.png[Local version control diagram]
 
-One of the more popular VCS tools was a system called RCS, which is still distributed with many computers today.
+One of the most popular VCS tool was a system called RCS, which is still distributed with many computers today.
 Even the popular Mac OS X operating system includes the `rcs` command when you install the Developer Tools.
 RCS works by keeping patch sets (that is, the differences between files) in a special format on disk; it can then re-create what any file looked like at any point in time by adding up all the patches.