diff --git a/sys/unix/configure.in b/sys/unix/configure.in
index e034edc..b62535d 100644
--- a/sys/unix/configure.in
+++ b/sys/unix/configure.in
@@ -83,8 +83,12 @@ AC_DEFINE_UNQUOTED(RMDIR_CMD, "$rmdir_cmd")
 dnl If the user wants canna support.
 AC_MSG_CHECKING(if --enable-canna option specified)
 AC_ARG_ENABLE(canna,
-	[  --enable-canna[=DIR]    Build a canna version.],
-	[cv_canna="yes"; cannapath=$enableval], [cv_canna="no"])
+	[  --enable-canna[=DIR]    Build a canna version.])
+AS_IF([test "x$enable_canna" != "xno"], [
+	cv_canna="yes"; cannapath=$enableval
+][
+	cv_canna="no";
+])
 AC_MSG_RESULT($cv_canna)
 if test "$cv_canna" = "yes"; then