diff --git a/src/INSTALL b/src/INSTALL
index a827fa1..99f1047 100644
--- a/src/INSTALL
+++ b/src/INSTALL
@@ -221,8 +221,8 @@
 be considered for the next release.  If at some point `config.cache'
 contains results you don't want to keep, you may remove or edit it.
 
-   The file `configure.in' is used to create `configure' by a program
-called `autoconf'.  You only need `configure.in' if you want to change
+   The file `configure.ac' is used to create `configure' by a program
+called `autoconf'.  You only need `configure.ac' if you want to change
 it or regenerate `configure' using a newer version of `autoconf'.
 
 The simplest way to compile this package is: