diff --git a/build/sync.sh b/build/sync.sh
index bc10401f..2491f1a6 100755
--- a/build/sync.sh
+++ b/build/sync.sh
@@ -44,9 +44,10 @@ DOCS_DIR=
 TMPMOUNT=/tmp/zealtmp
 
 print_usage() {
-	echo "Usage: $0 ( repo | vm ) [OPTION]"
+	echo "Usage: $0 ( repo | vm | diff ) [OPTION]"
 	echo "    repo             Overwrites src/ with virtual disk contents."
 	echo "    vm               Overwrites virtual disk with src/ contents."
+	echo "    diff             Runs a 'diff' between src/ and virtual disk."
 	echo "Options:"
 	echo "    --ignore-dots    Ignore dotfiles/dotfolders during synchronize."
 }
@@ -73,6 +74,12 @@ else
 	sudo modprobe nbd
 	[ ! -d $TMPMOUNT ] && mkdir $TMPMOUNT
 	case $1 in
+		diff)
+			mount_vdisk
+			diff -x *.MAP --color=always -r ../src/ $TMPMOUNT/ | less -R -p "diff -x.*|Only in.*"
+			umount_vdisk
+			echo "Finished."
+			;;
 		repo)
 			echo "Emptying src..."
 			rm -rf ../src/*