diff --git a/src/testdir/dumps/Test_smooth_diff_1.dump b/src/testdir/dumps/Test_smooth_diff_1.dump
new file mode 100644
index 0000000..4e2696e
--- /dev/null
+++ b/src/testdir/dumps/Test_smooth_diff_1.dump
@@ -0,0 +1,8 @@
+|-+0#0000e05#a8a8a8255| >j+0#0000000#ffffff0|u|s|t| |s|o|m|e| |t|e|x|t| |h|e|r|e| @53
+|~+0#4040ff13&| @73
+|~| @73
+|[+3#0000000&|N|o| |N|a|m|e|]| |[|+|]| @43|1|,|1| @11|A|l@1
+|-+0#0000e05#a8a8a8255| |j+0#0000000#ffffff0|u|s|t| |s|o|m|e| |t|e|x|t| |h|e|r|e| @53
+|~+0#4040ff13&| @73
+|[+1#0000000&|N|o| |N|a|m|e|]| |[|+|]| @43|1|,|1| @11|A|l@1
+| +0&&@74
diff --git a/src/testdir/test_scroll_opt.vim b/src/testdir/test_scroll_opt.vim
index 5dfc697..b114fe3 100644
--- a/src/testdir/test_scroll_opt.vim
+++ b/src/testdir/test_scroll_opt.vim
@@ -141,6 +141,32 @@
   call StopVimInTerminal(buf)
 endfunc
 
+func Test_smoothscroll_diff_mode()
+  CheckScreendump
+
+  let lines =<< trim END
+      vim9script
+      var text = 'just some text here'
+      setline(1, text)
+      set smoothscroll
+      diffthis
+      new
+      setline(1, text)
+      set smoothscroll
+      diffthis
+  END
+  call writefile(lines, 'XSmoothDiff', 'D')
+  let buf = RunVimInTerminal('-S XSmoothDiff', #{rows: 8})
+
+  call VerifyScreenDump(buf, 'Test_smooth_diff_1', {})
+  call term_sendkeys(buf, "\<C-Y>")
+  call VerifyScreenDump(buf, 'Test_smooth_diff_1', {})
+  call term_sendkeys(buf, "\<C-E>")
+  call VerifyScreenDump(buf, 'Test_smooth_diff_1', {})
+
+  call StopVimInTerminal(buf)
+endfunc
+
 
 
 " vim: shiftwidth=2 sts=2 expandtab