1 files changed, 6 insertions, 1 deletions
diff --git a/configure.in b/configure.in
index ec87736095..3f810bd1a8 100644
--- a/configure.in
+++ b/configure.in
@@ -88,7 +88,12 @@ AC_CONFIG_SUBDIRS($add_ons)
 add_ons_pfx=
 if test x"$add_ons" != x; then
   for f in $add_ons; do
-    add_ons_pfx="$add_ons_pfx $f/"
+    # Test whether such a subdir really exists.
+    if test -d $srcdir/$f; then
+      add_ons_pfx="$add_ons_pfx $f/"
+    else
+      AC_MSG_ERROR(add-on directory \"$f\" does not exist)
+    fi
   done
 fi