diff --git a/SheepShaver/src/Unix/configure.in b/SheepShaver/src/Unix/configure.in
index 6f684980..e46b67d8 100644
--- a/SheepShaver/src/Unix/configure.in
+++ b/SheepShaver/src/Unix/configure.in
@@ -53,7 +53,7 @@ x/* | x.*)
   mon_srcdir=$WANT_MON
   WANT_MON=yes
   ;;
-yes)
+xyes)
   mon_srcdir=../../../mon/src
   ;;
 esac