diff --git a/src/testdir/test_viminfo.vim b/src/testdir/test_viminfo.vim
index 264baa1..97fd7f7 100644
--- a/src/testdir/test_viminfo.vim
+++ b/src/testdir/test_viminfo.vim
@@ -214,6 +214,19 @@
   call assert_equal(l, getreg('d', 1, 1))
   call assert_equal("V", getregtype('d'))
 
+  " Length around 440 switches to line continuation.
+  let len = 434
+  while len < 445
+    let s = repeat('a', len)
+    call setreg('"', s)
+    wviminfo Xviminfo
+    call setreg('"', '')
+    rviminfo Xviminfo
+    call assert_equal(s, getreg('"'), 'wrong register at length: ' . len)
+
+    let len += 1
+  endwhile
+
   call delete('Xviminfo')
 endfunc