diff --git a/autoload/sy.vim b/autoload/sy.vim
index 3d2624a..5f187ef 100644
--- a/autoload/sy.vim
+++ b/autoload/sy.vim
@@ -3,23 +3,9 @@
 scriptencoding utf-8
 
 " Init: values {{{1
-let g:signify_sign_overwrite = get(g:, 'signify_sign_overwrite')
-if g:signify_sign_overwrite && (v:version < 703 || (v:version == 703 && !has('patch596')))
-  echohl WarningMsg
-  echomsg 'signify: Sign overwriting was disabled. See :help signify-option-sign_overwrite'
-  echohl NONE
-  let g:signify_sign_overwrite = 0
-endif
-
-if !exists('g:signify_skip_filetype')
-  let g:signify_skip_filetype = { 'help': 1 }
-endif
-
 let g:id_top = 0x100
 let g:sy_cache = {}
 
-sign define SignifyPlaceholder text=. texthl=SignifySignChange linehl=
-
 " Function: #start {{{1
 function! sy#start(path) abort
   if g:signify_locked
@@ -37,7 +23,14 @@ function! sy#start(path) abort
 
   " new buffer.. add to list of registered files
   if !exists('b:sy') || b:sy.path != a:path
-    let b:sy = { 'path': a:path, 'buffer': bufnr(''), 'active': 0, 'type': 'unknown', 'hunks': [], 'id_top': g:id_top, 'stats': [-1, -1, -1] }
+    let b:sy = {
+          \ 'path'  : a:path,
+          \ 'buffer': bufnr(''),
+          \ 'active': 0,
+          \ 'type'  : 'unknown',
+          \ 'hunks' : [],
+          \ 'id_top': g:id_top,
+          \ 'stats' : [-1, -1, -1] }
     if get(g:, 'signify_disable_by_default')
       return
     endif
@@ -78,55 +71,42 @@ function! sy#start(path) abort
   " update signs
   else
     let diff = sy#repo#get_diff_{b:sy.type}()[1]
-    if empty(diff)
-      call sy#sign#remove_all(b:sy.buffer)
-      return
-    endif
     let b:sy.id_top = g:id_top
   endif
 
   if get(g:, 'signify_line_highlight')
-      call sy#highlight#line_enable()
-  else
-      call sy#highlight#line_disable()
+    call sy#highlight#line_enable()
+  else 
+    call sy#highlight#line_disable()
   endif
 
-  execute 'sign place 99999 line=1 name=SignifyPlaceholder buffer='. b:sy.buffer
-  call sy#sign#remove_all(b:sy.buffer)
-
-  if !g:signify_sign_overwrite
-    call sy#sign#get_others()
-  endif
-
-  call sy#repo#process_diff(diff)
-  sign unplace 99999
+  call sy#sign#process_diff(diff)
 
   let b:sy.id_top = (g:id_top - 1)
 endfunction
 
 " Function: #stop {{{1
-function! sy#stop(bnum) abort
-  let bvars = getbufvar(a:bnum, '')
-  if empty(bvars) || !has_key(bvars, 'sy')
+function! sy#stop() abort
+  if !exists('b:sy')
     return
   endif
 
-  call sy#sign#remove_all(a:bnum)
+  call sy#sign#remove_all_signs()
 
   augroup signify
-    execute 'autocmd! * <buffer='. a:bnum .'>'
+    execute printf('autocmd! * <buffer=%d>', b:sy.buffer)
   augroup END
 endfunction
 
 " Function: #toggle {{{1
 function! sy#toggle() abort
-  if !exists('b:sy') || empty(b:sy.path)
+  if !exists('b:sy')
     echomsg 'signify: I cannot sy empty buffers!'
     return
   endif
 
   if b:sy.active
-    call sy#stop(b:sy.buffer)
+    call sy#stop()
     let b:sy.active = 0
     let b:sy.stats = [-1, -1, -1]
   else
diff --git a/autoload/sy/repo.vim b/autoload/sy/repo.vim
index 6f0d363..7d0db09 100644
--- a/autoload/sy/repo.vim
+++ b/autoload/sy/repo.vim
@@ -3,8 +3,6 @@
 scriptencoding utf-8
 
 " Init: values {{{1
-let s:sign_delete = get(g:, 'signify_sign_delete', '_')
-
 if !exists('g:signify_diffoptions')
   let g:signify_diffoptions = {}
 endif
@@ -171,148 +169,6 @@ function! sy#repo#get_diff_perforce() abort
   return v:shell_error ? [0, ''] : [1, diff]
 endfunction
 
-" Function: #process_diff {{{1
-function! sy#repo#process_diff(diff) abort
-  let added    = 0
-  let deleted  = 0
-  let modified = 0
-
-  " Determine where we have to put our signs.
-  for line in filter(split(a:diff, '\n'), 'v:val =~ "^@@ "')
-    let tokens = matchlist(line, '^@@ -\v(\d+),?(\d*) \+(\d+),?(\d*)')
-
-    let old_line = str2nr(tokens[1])
-    let new_line = str2nr(tokens[3])
-
-    let old_count = empty(tokens[2]) ? 1 : str2nr(tokens[2])
-    let new_count = empty(tokens[4]) ? 1 : str2nr(tokens[4])
-
-    let signs = []
-
-    " 2 lines added:
-
-    " @@ -5,0 +6,2 @@ this is line 5
-    " +this is line 5
-    " +this is line 5
-
-    if (old_count == 0) && (new_count >= 1)
-      let added += new_count
-      let offset = 0
-
-      while offset < new_count
-        call add(signs, {
-              \ 'type': 'SignifyAdd',
-              \ 'lnum': new_line + offset })
-        let offset += 1
-      endwhile
-
-    " 2 lines removed:
-
-    " @@ -6,2 +5,0 @@ this is line 5
-    " -this is line 6
-    " -this is line 7
-
-    elseif (old_count >= 1) && (new_count == 0)
-      let deleted += old_count
-
-      if new_line == 0
-        call add(signs, {
-              \ 'type': 'SignifyRemoveFirstLine',
-              \ 'lnum': 1 })
-      elseif old_count <= 99
-        call add(signs, {
-              \ 'type': 'SignifyDelete'. old_count,
-              \ 'text': substitute(s:sign_delete . old_count, '.*\ze..$', '', ''),
-              \ 'lnum': new_line })
-      else
-        call add(signs, {
-              \ 'type': 'SignifyDeleteMore',
-              \ 'lnum': new_line,
-              \ 'text': s:sign_delete .'>' })
-      endif
-
-    " 2 lines changed:
-
-    " @@ -5,2 +5,2 @@ this is line 4
-    " -this is line 5
-    " -this is line 6
-    " +this os line 5
-    " +this os line 6
-
-    elseif old_count == new_count
-      let modified += old_count
-      let offset    = 0
-
-      while offset < new_count
-        call add(signs, {
-              \ 'type': 'SignifyChange',
-              \ 'lnum': new_line + offset })
-        let offset += 1
-      endwhile
-    else
-
-      " 2 lines changed; 2 lines deleted:
-
-      " @@ -5,4 +5,2 @@ this is line 4
-      " -this is line 5
-      " -this is line 6
-      " -this is line 7
-      " -this is line 8
-      " +this os line 5
-      " +this os line 6
-
-      if old_count > new_count
-        let modified += new_count
-        let removed   = (old_count - new_count)
-        let deleted  += removed
-        let offset    = 0
-
-        while offset < (new_count - 1)
-          call add(signs, {
-                \ 'type': 'SignifyChange',
-                \ 'lnum': new_line + offset })
-          let offset += 1
-        endwhile
-
-        call add(signs, {
-              \ 'type': (removed > 9) ? 'SignifyChangeDeleteMore' : 'SignifyChangeDelete'. removed,
-              \ 'lnum': new_line })
-
-      " lines changed and added:
-
-      " @@ -5 +5,3 @@ this is line 4
-      " -this is line 5
-      " +this os line 5
-      " +this is line 42
-      " +this is line 666
-
-      else
-        let modified += old_count
-        let added    += (new_count - old_count)
-        let offset    = 0
-
-        while offset < old_count
-          call add(signs, {
-                \ 'type': 'SignifyChange',
-                \ 'lnum': new_line + offset })
-          let offset += 1
-        endwhile
-
-        while offset < new_count
-          call add(signs, {
-                \ 'type': 'SignifyAdd',
-                \ 'lnum': new_line + offset })
-          let offset += 1
-        endwhile
-      endif
-    endif
-
-    call sy#sign#set(signs)
-  endfor
-
-  let b:sy.stats = [added, modified, deleted]
-endfunction
-
 " Function: #get_stats {{{1
 function! sy#repo#get_stats() abort
   if !exists('b:sy') || !has_key(b:sy, 'stats')
diff --git a/autoload/sy/sign.vim b/autoload/sy/sign.vim
index c9d2d15..76147ff 100644
--- a/autoload/sy/sign.vim
+++ b/autoload/sy/sign.vim
@@ -3,71 +3,237 @@
 scriptencoding utf-8
 
 " Init: values {{{1
+let s:sign_delete      = get(g:, 'signify_sign_delete', '_')
 let s:delete_highlight = ['', 'SignifyLineDelete']
 
-" Function: #get_others {{{1
-function! sy#sign#get_others() abort
-  let s:other_signs_line_numbers = {}
+" Function: #get_next_id {{{1
+function! sy#sign#get_next_id() abort
+  let tmp = g:id_top
+  let g:id_top += 1
+  return tmp
+endfunction
+
+" Function: #get_current_signs {{{1
+function! sy#sign#get_current_signs() abort
+  let b:sy.internal = {}
+  let b:sy.external = {}
 
   let lang = v:lang
   silent! execute 'language message C'
-
   redir => signlist
     silent! execute 'sign place buffer='. b:sy.buffer
   redir END
-
-  let lines = filter(split(signlist, '\n'), 'v:val =~ "^\\s\\+line"')
-
-  if lines[0] =~ 99999
-    call remove(lines, 0)
-  endif
-
-  for line in lines
-    let lnum = matchlist(line, '\v^\s+line\=(\d+)')[1]
-    let s:other_signs_line_numbers[lnum] = 1
-  endfor
-
   silent! execute 'language message' lang
+
+  for signline in split(signlist, '\n')[2:]
+    let tokens = matchlist(signline, '\v^\s+line\=(\d+)\s+id\=(\d+)\s+name\=(.*)$')
+    let line   = str2nr(tokens[1])
+    let id     = str2nr(tokens[2])
+    let type   = tokens[3]
+
+    if type =~# '^Signify'
+      " Handle ambiguous signs. Assume you have signs on line 3 and 4.
+      " Removing line 3 would lead to the second sign to be shifted up
+      " to line 3. Now there are still 2 signs, both one line 3.
+      if has_key(b:sy.internal, line)
+        execute 'sign unplace' b:sy.internal[line].id
+      endif
+      let b:sy.internal[line] = { 'type': type, 'id': id }
+    else
+      let b:sy.external[line] = id
+    endif
+  endfor
 endfunction
 
-" Function: #set {{{1
-function! sy#sign#set(signs)
-  let hunk = { 'ids': [], 'start': a:signs[0].lnum, 'end': a:signs[-1].lnum }
 
-  for sign in a:signs
-    " Preserve non-signify signs
-    if !g:signify_sign_overwrite && has_key(s:other_signs_line_numbers, sign.lnum)
-      continue
-    endif
+" Function: #process_diff {{{1
+function! sy#sign#process_diff(diff) abort
+  let b:sy.signtable             = {}
+  let b:sy.hunks                 = []
+  let [added, modified, deleted] = [0, 0, 0]
 
-    call add(hunk.ids, g:id_top)
-    if sign.type =~# 'SignifyDelete'
-      execute 'sign define '. sign.type .' text='. sign.text .' texthl=SignifySignDelete linehl='. s:delete_highlight[g:signify_line_highlight]
-      execute 'sign place' g:id_top 'line='. sign.lnum 'name='. sign.type 'buffer='. b:sy.buffer
+  call sy#sign#get_current_signs()
+
+  " Determine where we have to put our signs.
+  for line in filter(split(a:diff, '\n'), 'v:val =~ "^@@ "')
+    let b:sy.lines = []
+    let ids        = []
+
+    let tokens = matchlist(line, '^@@ -\v(\d+),?(\d*) \+(\d+),?(\d*)')
+
+    let old_line = str2nr(tokens[1])
+    let new_line = str2nr(tokens[3])
+
+    let old_count = empty(tokens[2]) ? 1 : str2nr(tokens[2])
+    let new_count = empty(tokens[4]) ? 1 : str2nr(tokens[4])
+
+    " 2 lines added:
+
+    " @@ -5,0 +6,2 @@ this is line 5
+    " +this is line 5
+    " +this is line 5
+    if (old_count == 0) && (new_count >= 1)
+      let added += new_count
+      let offset = 0
+      while offset < new_count
+        let line    = new_line + offset
+        let offset += 1
+        if s:external_sign_present(line) | continue | endif
+        call add(ids, s:add_sign(line, 'SignifyAdd'))
+      endwhile
+
+    " 2 lines removed:
+
+    " @@ -6,2 +5,0 @@ this is line 5
+    " -this is line 6
+    " -this is line 7
+    elseif (old_count >= 1) && (new_count == 0)
+      if s:external_sign_present(new_line) | continue | endif
+      let deleted += old_count
+      if new_line == 0
+        call add(ids, s:add_sign(1, 'SignifyRemoveFirstLine'))
+      elseif old_count <= 99
+        call add(ids, s:add_sign(new_line, 'SignifyDelete'. old_count, substitute(s:sign_delete . old_count, '.*\ze..$', '', '')))
+      else
+        call add(ids, s:add_sign(new_line, 'SignifyDeleteMore', s:sign_delete .'>'))
+      endif
+
+    " 2 lines changed:
+
+    " @@ -5,2 +5,2 @@ this is line 4
+    " -this is line 5
+    " -this is line 6
+    " +this os line 5
+    " +this os line 6
+    elseif old_count == new_count
+      let modified += old_count
+      let offset    = 0
+      while offset < new_count
+        let line    = new_line + offset
+        let offset += 1
+        if s:external_sign_present(line) | continue | endif
+        call add(ids, s:add_sign(line, 'SignifyChange'))
+      endwhile
     else
-      execute 'sign place' g:id_top 'line='. sign.lnum 'name='. sign.type 'buffer='. b:sy.buffer
+
+      " 2 lines changed; 2 lines removed:
+
+      " @@ -5,4 +5,2 @@ this is line 4
+      " -this is line 5
+      " -this is line 6
+      " -this is line 7
+      " -this is line 8
+      " +this os line 5
+      " +this os line 6
+      if old_count > new_count
+        let modified += new_count
+        let removed   = old_count - new_count
+        let deleted  += removed
+        let offset    = 0
+        while offset < new_count - 1
+          let line    = new_line + offset
+          let offset += 1
+          if s:external_sign_present(line) | continue | endif
+          call add(ids, s:add_sign(line, 'SignifyChange'))
+        endwhile
+        let line = new_line + offset
+        if s:external_sign_present(line) | continue | endif
+        call add(ids, s:add_sign(line, (removed > 9) ? 'SignifyChangeDeleteMore' : 'SignifyChangeDelete'. removed))
+
+      " lines changed and added:
+
+      " @@ -5 +5,3 @@ this is line 4
+      " -this is line 5
+      " +this os line 5
+      " +this is line 42
+      " +this is line 666
+      else
+        let modified += old_count
+        let offset    = 0
+        while offset < old_count
+          let line    = new_line + offset
+          let offset += 1
+          if s:external_sign_present(line) | continue | endif
+          call add(ids, s:add_sign(line, 'SignifyChange'))
+          let added += 1
+        endwhile
+        while offset < new_count
+          let line    = new_line + offset
+          let offset += 1
+          if s:external_sign_present(line) | continue | endif
+          call add(ids, s:add_sign(line, 'SignifyAdd'))
+        endwhile
+      endif
     endif
 
-    let g:id_top += 1
+    if !empty(ids)
+      call add(b:sy.hunks, {
+            \ 'ids'  : ids,
+            \ 'start': b:sy.lines[0],
+            \ 'end'  : b:sy.lines[-1] })
+    endif
   endfor
 
-  call add(b:sy.hunks, hunk)
+  " Remove obsoleted signs.
+  for line in filter(keys(b:sy.internal), '!has_key(b:sy.signtable, v:val)')
+    execute 'sign unplace' b:sy.internal[line].id
+  endfor
+
+  let b:sy.stats = [added, modified, deleted]
 endfunction
 
-" Function: #remove_all {{{1
-function! sy#sign#remove_all(bnum) abort
-  let sy = getbufvar(a:bnum, 'sy')
+function! s:add_sign(line, type, ...) abort
+  call add(b:sy.lines, a:line)
+  let b:sy.signtable[a:line] = 1
 
-  if g:signify_sign_overwrite
-    execute 'sign unplace * buffer='. sy.buffer
-  else
-    for hunk in sy.hunks
-      for id in hunk.ids
-        execute 'sign unplace' id
-      endfor
-    endfor
+  if has_key(b:sy.internal, a:line)
+    " There is a sign on this line already.
+    if a:type == b:sy.internal[a:line].type
+      " Keep current sign since the new one is of the same type.
+      return b:sy.internal[a:line].id
+    else
+      " Update sign by overwriting the ID of the current sign.
+      let id = b:sy.internal[a:line].id
+    endif
   endif
 
-  let sy.hunks = []
-  let sy.stats = [0, 0, 0]
+  if !exists('id')
+    let id = sy#sign#get_next_id()
+  endif
+
+  if a:type =~# 'SignifyDelete'
+    execute printf('sign define %s text=%s texthl=SignifySignDelete linehl=%s',
+          \ a:type,
+          \ a:1,
+          \ s:delete_highlight[g:signify_line_highlight])
+  endif
+  execute printf('sign place %d line=%d name=%s buffer=%s',
+        \ id,
+        \ a:line,
+        \ a:type,
+        \ b:sy.buffer)
+
+  return id
+endfunction
+
+function! s:external_sign_present(line) abort
+  if has_key(b:sy.external, a:line)
+    if has_key(b:sy.internal, a:line)
+      " Remove Sy signs from lines with other signs.
+      execute 'sign unplace' b:sy.internal[a:line].id
+    endif
+    return 1
+  endif
+endfunction
+
+" Function: #remove_all_signs {{{1
+function! sy#sign#remove_all_signs() abort
+  for hunk in b:sy.hunks
+    for id in hunk.ids
+      execute 'sign unplace' id
+    endfor
+  endfor
+
+  let b:sy.hunks = []
+  let b:sy.stats = [0, 0, 0]
 endfunction
diff --git a/autoload/sy/util.vim b/autoload/sy/util.vim
index 17b7e8e..a6ca6c0 100644
--- a/autoload/sy/util.vim
+++ b/autoload/sy/util.vim
@@ -30,12 +30,14 @@ endfunction
 " Function: #run_in_dir {{{1
 function! sy#util#run_in_dir(dir, cmd) abort
   let chdir = haslocaldir() ? 'lcd' : 'cd'
-  let cwd = getcwd()
+  let cwd   = getcwd()
+
   try
-    exe chdir .' '. fnameescape(fnamemodify(a:dir, ':p'))
-    let resp = system(a:cmd)
+    execute chdir fnameescape(fnamemodify(a:dir, ':p'))
+    let ret = system(a:cmd)
   finally
-    exe chdir .' '. fnameescape(cwd)
+    execute chdir fnameescape(cwd)
   endtry
-  return resp
+
+  return ret
 endfunction
diff --git a/doc/signify.txt b/doc/signify.txt
index 80eca91..baa137b 100644
--- a/doc/signify.txt
+++ b/doc/signify.txt
@@ -94,7 +94,6 @@ All available options:~
     |g:signify_mapping_toggle|
     |g:signify_skip_filetype|
     |g:signify_skip_filename|
-    |g:signify_sign_overwrite|
     |g:signify_update_on_bufenter|
     |g:signify_update_on_focusgained|
     |g:signify_line_highlight|
@@ -194,21 +193,6 @@ NOTE: Filenames have to be absolute paths.
 
 Default: Both are empty.
 
-------------------------------------------------------------------------------
-                                                      *g:signify_sign_overwrite*
->
-    let g:signify_sign_overwrite = 0
-<
-Setting this to 1 means that Sy doesn't have to manage its signs and just
-removes ALL signs before adding its own signs. This typically results
-in a tad more performance, especially when a lot of signs are in use.
-
-If you need plugin compatibility though, you should set this to 0. In this
-case Sy will remember which signs it set last and only removes those at the
-next update.
-
-NOTE: This feature needs at least Vim 7.3.596!
-
 ------------------------------------------------------------------------------
                                                   *g:signify_update_on_bufenter*
 >
diff --git a/plugin/signify.vim b/plugin/signify.vim
index 460683f..ad5366b 100644
--- a/plugin/signify.vim
+++ b/plugin/signify.vim
@@ -2,10 +2,11 @@
 
 scriptencoding utf-8
 
-if exists('g:loaded_signify') || !has('signs') || &cp
+if exists('g:loaded_signify') || !has('signs') || &compatible
   finish
 endif
 
+" Init: values {{{1
 let g:loaded_signify = 1
 let g:signify_locked = 0
 
@@ -16,34 +17,26 @@ augroup signify
   autocmd VimEnter                         * call sy#highlight#setup()
   autocmd BufRead,BufEnter,SessionLoadPost * let b:sy_path = resolve(expand('<afile>:p'))
   autocmd BufRead,BufWritePost             * call sy#start(b:sy_path)
-  autocmd BufDelete                        * call sy#stop(expand('<abuf>'))
+  autocmd BufDelete                        * call sy#stop()
 
   autocmd QuickFixCmdPre  *vimgrep* let g:signify_locked = 1
   autocmd QuickFixCmdPost *vimgrep* let g:signify_locked = 0
 
   if get(g:, 'signify_update_on_bufenter')
-    autocmd BufEnter * nested
-          \ if exists('b:sy') && b:sy.active && &modified |
-          \   write |
-          \ endif
+    autocmd BufEnter * nested call s:save()
   endif
-
   if get(g:, 'signify_cursorhold_normal')
-    autocmd CursorHold * nested
-          \ if exists('b:sy') && b:sy.active && &modified |
-          \   write |
-          \ endif
+    autocmd CursorHold * nested call s:save()
   endif
-
   if get(g:, 'signify_cursorhold_insert')
-    autocmd CursorHoldI * nested
-          \ if exists('b:sy') && b:sy.active && &modified |
-          \   write |
-          \ endif
+    autocmd CursorHoldI * nested call s:save()
   endif
 
   if get(g:, 'signify_update_on_focusgained') && !has('gui_win32')
-    autocmd FocusGained * if exists('b:sy') | call sy#start(b:sy.path) | endif
+    autocmd FocusGained *
+          \ if exists('b:sy') |
+          \   call sy#start(b:sy.path) |
+          \ endif
   endif
 augroup END
 
@@ -89,3 +82,10 @@ endif
 if empty(maparg('[c', 'n'))
   nmap [c <plug>(signify-prev-hunk)
 endif
+
+" Function: save {{{1
+function! s:save()
+  if exists('b:sy') && b:sy.active && &modified
+    write
+  endif
+endfunction