diff --git a/weak-modules b/weak-modules
index db1839c..dd163cc 100644
--- a/weak-modules
+++ b/weak-modules
@@ -468,7 +468,7 @@ prepare_sandbox() {
 
     #config
     echo "search external extra built-in weak-updates" >"$conf"
-    echo "external $krel $dir" >>"$conf"
+    echo "external * $dir" >>"$conf"
 
     depmod="$depmod_orig -C $conf"
 }
@@ -966,6 +966,7 @@ add_kernel() {
     local krel=${1:-$(uname -r)}
     local tmp
     local no_force_update=""
+    local num
 
     tmp=$(mktemp -p $tmpdir)
 
@@ -983,9 +984,28 @@ add_kernel() {
 
         # reuse tmp
 
+	# optimization, check independent modules in one run.
+	# first try groups with one element in each.
+	# it means independent modules, so we can safely remove
+	# incompatible links
+	# some cut and paste here
+
+	echo > $tmp
         for g in "${groups[@]}"; do
+	    num="$(echo "$g" | wc -w)"
+	    [ "$num" -gt 1 ] && continue
+
+            printf '%s\n' $g >> $tmp
+	done
+        # to avoid subshell, see the read_modules_list comment
+        read_modules_list < $tmp
+        update_modules_for_krel $krel add_weak_links force_update
+
+        for g in "${groups[@]}"; do
+	    num="$(echo "$g" | wc -w)"
+	    [ "$num" -eq 1 ] && continue
+
             printf '%s\n' $g > $tmp
-            # to avoid subshell, see the read_modules_list comment
             read_modules_list < $tmp
             update_modules_for_krel $krel add_weak_links $no_force_update
         done