diff --git a/src/nvim/undo.c b/src/nvim/undo.c
index 960b6bd264..9810e30f21 100644
--- a/src/nvim/undo.c
+++ b/src/nvim/undo.c
@@ -1565,36 +1565,48 @@ void u_read_undo(char *name, const uint8_t *hash, const char *orig_name FUNC_ATT
         goto error;
       }
     }
-    for (int j = 0; j < num_head; j++) {
-      if (uhp_table[j] != NULL
-          && uhp_table[j]->uh_seq == uhp->uh_next.seq) {
-        uhp->uh_next.ptr = uhp_table[j];
-        SET_FLAG(j);
-        break;
+    {
+      const int seq = uhp->uh_next.seq;
+      uhp->uh_next.ptr = NULL;
+      for (int j = 0; j < num_head; j++) {
+        if (uhp_table[j] != NULL && i != j && uhp_table[j]->uh_seq == seq) {
+          uhp->uh_next.ptr = uhp_table[j];
+          SET_FLAG(j);
+          break;
+        }
       }
     }
-    for (int j = 0; j < num_head; j++) {
-      if (uhp_table[j] != NULL
-          && uhp_table[j]->uh_seq == uhp->uh_prev.seq) {
-        uhp->uh_prev.ptr = uhp_table[j];
-        SET_FLAG(j);
-        break;
+    {
+      const int seq = uhp->uh_prev.seq;
+      uhp->uh_prev.ptr = NULL;
+      for (int j = 0; j < num_head; j++) {
+        if (uhp_table[j] != NULL && i != j && uhp_table[j]->uh_seq == seq) {
+          uhp->uh_prev.ptr = uhp_table[j];
+          SET_FLAG(j);
+          break;
+        }
       }
     }
-    for (int j = 0; j < num_head; j++) {
-      if (uhp_table[j] != NULL
-          && uhp_table[j]->uh_seq == uhp->uh_alt_next.seq) {
-        uhp->uh_alt_next.ptr = uhp_table[j];
-        SET_FLAG(j);
-        break;
+    {
+      const int seq = uhp->uh_alt_next.seq;
+      uhp->uh_alt_next.ptr = NULL;
+      for (int j = 0; j < num_head; j++) {
+        if (uhp_table[j] != NULL && i != j && uhp_table[j]->uh_seq == seq) {
+          uhp->uh_alt_next.ptr = uhp_table[j];
+          SET_FLAG(j);
+          break;
+        }
       }
     }
-    for (int j = 0; j < num_head; j++) {
-      if (uhp_table[j] != NULL
-          && uhp_table[j]->uh_seq == uhp->uh_alt_prev.seq) {
-        uhp->uh_alt_prev.ptr = uhp_table[j];
-        SET_FLAG(j);
-        break;
+    {
+      const int seq = uhp->uh_alt_prev.seq;
+      uhp->uh_alt_prev.ptr = NULL;
+      for (int j = 0; j < num_head; j++) {
+        if (uhp_table[j] != NULL && i != j && uhp_table[j]->uh_seq == seq) {
+          uhp->uh_alt_prev.ptr = uhp_table[j];
+          SET_FLAG(j);
+          break;
+        }
       }
     }
     if (old_header_seq > 0 && old_idx < 0 && uhp->uh_seq == old_header_seq) {
diff --git a/test/old/testdir/test_undo.vim b/test/old/testdir/test_undo.vim
index fe3d5f8209..2527c43f40 100644
--- a/test/old/testdir/test_undo.vim
+++ b/test/old/testdir/test_undo.vim
@@ -924,4 +924,43 @@ func Test_restore_cursor_position_after_undo()
 endfunc
 
 
+" Corrupted undo file via cyclic cross-references caused
+" double free
+func Test_corrupted_undofile()
+  CheckFeature persistent_undo
+  let _uf = &undofile
+  set undofile
+  new
+  call setline(1, 'hello')
+  let b=eval('0z56696D9F556E446FE50002F3AEFE62965A91903610' ..
+           \ 'F0E23CC8A69D5B87CEA6D28E75489B0D2CA02ED7993C' ..
+           \ '00000001000000000000000000000000000000010000' ..
+           \ '00010000000100000001000000010000000100000000' ..
+           \ '3B9ACA00005FD0000000010000000000000000000000' ..
+           \ '00000000010000000100000000000000000000000000' ..
+           \ '00000000000000000000000000000000000000000000' ..
+           \ '00000000000000000000000000000000000000000000' ..
+           \ '00000000000000000000000000000000000000000000' ..
+           \ '00000000000000000000000000000000000000000000' ..
+           \ '00000000000000000000000000000000000000000000' ..
+           \ '00000000000000000000000000000000000000000000' ..
+           \ '00000000000000000000000000000000000000000000' ..
+           \ '00000000000000000000000000000000000000000000' ..
+           \ '00000000000000000000000000000000000000000000' ..
+           \ '00000000000000000000000000000000000000000000' ..
+           \ '00000000000000000000000000000000000000000000' ..
+           \ '00000000000000000000000000000000000000000000' ..
+           \ '00000000000000000000000000000000000000000000' ..
+           \ '00000000000000000000000000000000000000000000' ..
+           \ '00000000000000000000000000000000000000000000' ..
+           \ '000000000000000000000000000000000000003B9ACA' ..
+           \ '00003581E7AA')
+  " Nvim: convert undo file format
+  let b = b->slice(0, -2) + 0z3581 + b->slice(-2) | let b[10] = 0x03
+  call writefile(b, 'Xundo', 'bD')
+  rundo Xundo
+  bw!
+  let &undofile = _uf
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab