diff --git a/compat/winansi.c b/compat/winansi.c
index 82b89ab13767a5e562d4f41826d98bce0d704e1c..793420f9d0d7732cb7dc2aa94845a22086fe7021 100644
--- a/compat/winansi.c
+++ b/compat/winansi.c
@@ -510,6 +510,8 @@ static HANDLE swap_osfhnd(int fd, HANDLE new_handle)
 	 */
 	close(new_fd);
 
+	if (fd == 2)
+		setvbuf(stderr, NULL, _IONBF, BUFSIZ);
 	fd_is_interactive[fd] |= FD_SWAPPED;
 
 	return duplicate;
@@ -547,6 +549,8 @@ static void detect_msys_tty(int fd)
 			!wcsstr(name, L"-pty"))
 		return;
 
+	if (fd == 2)
+		setvbuf(stderr, NULL, _IONBF, BUFSIZ);
 	fd_is_interactive[fd] |= FD_MSYS;
 }