diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 7f745a5..8ef9f50 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -14,7 +14,7 @@ jobs:
     steps:
     - uses: actions/checkout@v2
     - name: install dependencies
-      run: sudo apt-get install txt2man pkg-config libglib2.0-dev libgtk-3-dev libnotify-dev libgee-0.8-dev lua5.1 moreutils xdelta
+      run: sudo apt-get install txt2man pkg-config libglib2.0-dev libgtk-3-dev libnotify-dev libgee-0.8-dev lua5.1 moreutils xdelta3
     - name: build
       run: make
     - name: test
diff --git a/Makefile b/Makefile
index a2cbdfd..6aaec1c 100644
--- a/Makefile
+++ b/Makefile
@@ -36,7 +36,7 @@ H=@
 
 PREFIX=usr/local
 SED=sed
-XDELTA=xdelta
+XDELTA=xdelta3
 SSH=ssh
 LUAV=5.1
 LUA=lua$(LUAV)
@@ -150,7 +150,7 @@ define install-replacing
 		$(SED) 's?@XDELTA@?$(XDELTA)?' |\
 		$(SED) 's?@SSH@?$(SSH)?' |\
 		$(SED) 's?@SMDVERSION@?$(VERSION)?' |\
-		$(SED) 's?#! /usr/bin/env lua.*?#! /usr/bin/env $(LUA)?' |\
+		$(SED) 's?#!/usr/bin/env lua.*?#!/usr/bin/env $(LUA)?' |\
 		cat > $(DESTDIR)/$(PREFIX)/$(2)/$(1)
 	if [ $(2) = "bin" ]; then chmod a+rx $(DESTDIR)/$(PREFIX)/$(2)/$(1); fi
 endef
diff --git a/README.md b/README.md
index 2e6b520..24775ef 100644
--- a/README.md
+++ b/README.md
@@ -453,7 +453,7 @@ supported by templates defined at the end of `Makefile`, for example you may
 want to run `make osx/text/all && make osx/text/install` to properly build and
 install text mode only syncmaildir utilities on an MacOSX platform.
 
-Runtime dependencies are: `ssh`, `xdelta`, `lua5.1` and `bash`.
+Runtime dependencies are: `ssh`, `xdelta3`, `lua5.1` and `bash`.
 
 Design
 ======
diff --git a/smd-client b/smd-client
index 59f9fdf..fe4593b 100755
--- a/smd-client
+++ b/smd-client
@@ -1,4 +1,4 @@
-#! /usr/bin/env lua5.1
+#!/usr/bin/env lua5.1
 -- 
 -- Released under the terms of GPLv3 or at your option any later version.
 -- No warranties.
@@ -762,7 +762,7 @@ function main()
 
 	local rc
 	if not dry_run() and apply_xdelta then
-		rc = os.execute(XDELTA..' patch '..xdelta..' '..dbfile..' '..newdb)
+		rc = os.execute(XDELTA..' -d -s '..dbfile..' '..xdelta..' '..newdb)
 	else
 		rc = 0 -- the xdelta transmitted with --dry-run is dummy
 	end
diff --git a/smd-server b/smd-server
index 947a057..fd80ebd 100755
--- a/smd-server
+++ b/smd-server
@@ -1,4 +1,4 @@
-#! /usr/bin/env lua5.1
+#!/usr/bin/env lua5.1
 -- 
 -- Released under the terms of GPLv3 or at your option any later version.
 -- No warranties.
@@ -162,7 +162,7 @@ function main()
 			local rc
 			if not dry_run() then
 				rc = os.execute(
-					XDELTA..' delta '..dbfile..' '..newdb..' '..xdelta)
+					XDELTA..' -e -s '..dbfile..' '..newdb..' '..xdelta)
 			else
 				local f = io.open(xdelta,'w')
 				f:close()
diff --git a/syncmaildir.lua b/syncmaildir.lua
index 33177f2..466943b 100644
--- a/syncmaildir.lua
+++ b/syncmaildir.lua
@@ -31,7 +31,7 @@ end
 -- set xdelta executable name
 XDELTA = '@XDELTA@'
 if string.sub(XDELTA,1,1) == '@' then
-		XDELTA = 'xdelta'
+		XDELTA = 'xdelta3'
 end
 
 -- set smd version