diff --git a/compat/winansi.c b/compat/winansi.c
index cb725fb02f..97d84a96ed 100644
--- a/compat/winansi.c
+++ b/compat/winansi.c
@@ -556,7 +556,7 @@ static void detect_msys_tty(int fd)
 			buffer, sizeof(buffer) - 2, &result)))
 		return;
 	name = nameinfo->Name.Buffer;
-	name[nameinfo->Name.Length] = 0;
+	name[nameinfo->Name.Length / sizeof(*name)] = 0;
 
 	/* check if this could be a MSYS2 pty pipe ('msys-XXXX-ptyN-XX') */
 	if (!wcsstr(name, L"msys-") || !wcsstr(name, L"-pty"))