diff --git a/src/win/tty.c b/src/win/tty.c
index b0f0031c5..9e79d5f9d 100644
--- a/src/win/tty.c
+++ b/src/win/tty.c
@@ -555,6 +555,7 @@ static DWORD CALLBACK uv_tty_line_read_thread(void* data) {
                                       NULL);
 
   if (read_console_success) {
+   assert(bytes > 0);
     read_bytes = bytes - 1;
     uv_utf16_to_wtf8(utf16,
                      read_chars,