diff --git a/target/default/target_skeleton/bin/ipkg b/target/default/target_skeleton/bin/ipkg
index 19454192b8..6ceb9d4574 100755
--- a/target/default/target_skeleton/bin/ipkg
+++ b/target/default/target_skeleton/bin/ipkg
@@ -21,8 +21,8 @@ set -o noglob
 
 ipkg_is_upgrade () {
   local A B a b
-  A=$(echo $1 | sed "s/[0-9]*/ & /g")
-  B=$(echo $2 | sed "s/[0-9]*/ & /g")
+  A=$(echo $1 | sed "s/[0-9]*/ & /g" | sed "s/[^ A-Za-z0-9]//g")
+  B=$(echo $2 | sed "s/[0-9]*/ & /g" | sed "s/[^ A-Za-z0-9]//g")
   while [ \! -z "$A" ] && [ \! -z "$B" ]; do {
     set $A; a=$1; shift; A=$*
     set $B; b=$1; shift; B=$*