2 files changed, 8 insertions, 0 deletions
diff --git a/src/nvim/ex_cmds.c b/src/nvim/ex_cmds.c
index a0618ce7d7..4f6b8f2c8f 100644
--- a/src/nvim/ex_cmds.c
+++ b/src/nvim/ex_cmds.c
@@ -3888,6 +3888,10 @@ static int do_sub(exarg_T *eap, const proftime_T timeout, const long cmdpreview_
           nmatch = curbuf->b_ml.ml_line_count - sub_firstlnum + 1;
           current_match.end.lnum = sub_firstlnum + (linenr_T)nmatch;
           skip_match = true;
+          // safety check
+          if (nmatch < 0) {
+            goto skip;
+          }
         }
 
         // Save the line numbers for the preview buffer
diff --git a/src/nvim/window.c b/src/nvim/window.c
index e72c32700d..9d804ecae7 100644
--- a/src/nvim/window.c
+++ b/src/nvim/window.c
@@ -1884,6 +1884,10 @@ static void win_exchange(int Prenum)
     beep_flush();
     return;
   }
+  if (text_or_buf_locked()) {
+    beep_flush();
+    return;
+  }
 
   frame_T *frp;