diff --git a/pscp.c b/pscp.c
index 69e1e40e..695ace3d 100644
--- a/pscp.c
+++ b/pscp.c
@@ -811,6 +811,15 @@ int scp_send_filedata(char *data, int len)
         }
 
         while (!xfer_upload_ready(scp_sftp_xfer)) {
+            if (toplevel_callback_pending()) {
+                /* If we have pending callbacks, they might make
+                 * xfer_upload_ready start to return true. So we should
+                 * run them and then re-check xfer_upload_ready, before
+                 * we go as far as waiting for an entire packet to
+                 * arrive. */
+                run_toplevel_callbacks();
+                continue;
+            }
             pktin = sftp_recv();
             ret = xfer_upload_gotpkt(scp_sftp_xfer, pktin);
             if (ret <= 0) {
diff --git a/psftp.c b/psftp.c
index 8399ac07..2be47894 100644
--- a/psftp.c
+++ b/psftp.c
@@ -725,6 +725,16 @@ bool sftp_put_file(char *fname, char *outfname, bool recurse, bool restart)
             }
         }
 
+        if (toplevel_callback_pending() && !err && !eof) {
+            /* If we have pending callbacks, they might make
+             * xfer_upload_ready start to return true. So we should
+             * run them and then re-check xfer_upload_ready, before
+             * we go as far as waiting for an entire packet to
+             * arrive. */
+            run_toplevel_callbacks();
+            continue;
+        }
+
         if (!xfer_done(xfer)) {
             pktin = sftp_recv();
             ret = xfer_upload_gotpkt(xfer, pktin);