diff --git a/icp b/icp
index 599dc12..c6d3e3b 100755
--- a/icp
+++ b/icp
@@ -3,6 +3,7 @@ usage() {
   echo >&2 "Usage: $(basename $0) [OPTION] SOURCE... DEST"
   echo >&2 "Copy like cp, but use rsync in the background."
   echo >&2 "Options:"
+  echo >&2 " -c          only transfer files whos checksum does not match"
   echo >&2 " -h          print this help message"
   echo >&2 " -L          follow symlinks in source"
   echo >&2 " -n          no-clobber, do not overwrite existing files"
@@ -33,6 +34,8 @@ do
   elif [[ "$arg" == "-r" ]];then
     flag_recursive=1
     rsync_opt+=("-r")
+  elif [[ "$arg" == "-c" ]];then
+    rsync_opt+=("-c")
   elif [[ "$arg" == "-L" ]];then
     rsync_opt+=("-L")
   elif [[ "$arg" == "-v" ]];then