diff --git a/tests/defs.in b/tests/defs.in
index d79d874..e4bc755 100644
--- a/tests/defs.in
+++ b/tests/defs.in
@@ -299,11 +299,15 @@ case $required in
     aclocaldir='@prefix@/share/aclocal'
     extra_includes=""
     if test -f $aclocaldir/dirlist; then
-       extra_includes=`(tmp_inc=""
-       while read LINE ; do
-	  tmp_inc="$tmp_inc -I $LINE"
-       done
-       echo $tmp_inc) < $aclocaldir/dirlist`
+       extra_includes=`
+       sed -ne 's/#.*//;/[^	 ]/p' $aclocaldir/dirlist |
+       (
+	   tmp_inc=""
+	   while read LINE ; do
+	       tmp_inc="$tmp_inc -I $LINE"
+	   done
+	   echo $tmp_inc
+       )`
     else :; fi
 
     libtool_found=no