diff --git a/src/nvim/diff.c b/src/nvim/diff.c
index cb1576971d..bc69314f4f 100644
--- a/src/nvim/diff.c
+++ b/src/nvim/diff.c
@@ -3822,9 +3822,12 @@ static void diffgetput(const int addr_count, const int idx_cur, const int idx_fr
     bool did_free = false;
     linenr_T lnum = dp->df_lnum[idx_to];
     linenr_T count = dp->df_count[idx_to];
+    // The empty line of an empty buffer is deleted below, include it in
+    // the undo information, otherwise undo leaves a line behind.
+    linenr_T undo_bot = lnum + count + (count == 0 && buf_is_empty(curbuf) ? 1 : 0);
 
     if ((dp->df_lnum[idx_cur] + dp->df_count[idx_cur] > line1 + off)
-        && (u_save(lnum - 1, lnum + count) != FAIL)) {
+        && (u_save(lnum - 1, undo_bot) != FAIL)) {
       // Inside the specified range and saving for undo worked.
       linenr_T start_skip = 0;
       linenr_T end_skip = 0;
diff --git a/test/old/testdir/test_diffmode.vim b/test/old/testdir/test_diffmode.vim
index b5e2c886ba..2733ffc36b 100644
--- a/test/old/testdir/test_diffmode.vim
+++ b/test/old/testdir/test_diffmode.vim
@@ -253,6 +253,24 @@ func Test_diffget_diffput()
   %bwipe!
 endfunc
 
+" Undo after getting lines into an empty buffer must leave it empty again
+func Test_diffget_undo_empty_buffer()
+  enew!
+  diffthis
+  new
+  call setline(1, ['1', '2'])
+  diffthis
+
+  wincmd p
+  normal do
+  call assert_equal(['1', '2'], getline(1, '$'))
+  undo
+  call assert_equal([''], getline(1, '$'))
+
+  windo diffoff
+  %bwipe!
+endfunc
+
 " Test putting two changes from one buffer to another
 func Test_diffput_two()
   new a