diff --git a/src/blowfish.c b/src/blowfish.c
index ac9b088..eaf0b9e 100644
--- a/src/blowfish.c
+++ b/src/blowfish.c
@@ -38,7 +38,7 @@
   /* MS-Windows is always little endian */
 #else
 # ifdef HAVE_CONFIG_H
-   /* in configure.in AC_C_BIGENDIAN() defines WORDS_BIGENDIAN when needed */
+   /* in configure.ac AC_C_BIGENDIAN() defines WORDS_BIGENDIAN when needed */
 # else
    error!
    Please change this code to define WORDS_BIGENDIAN for big-endian machines.