From 1b0dcd400717b3ced323a66c525371ed1b928cbf Mon Sep 17 00:00:00 2001
From: Andrew Kelley <andrew@ziglang.org>
Date: Thu, 23 Oct 2025 04:27:10 -0700
Subject: [PATCH] std.Io.Threaded: fix setting of O_NONBLOCK flag

---
 lib/std/Io/Threaded.zig | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/std/Io/Threaded.zig b/lib/std/Io/Threaded.zig
index c1365e0f44..8b880a176f 100644
--- a/lib/std/Io/Threaded.zig
+++ b/lib/std/Io/Threaded.zig
@@ -1651,7 +1651,7 @@ fn dirCreateFilePosix(
                 else => |err| return posix.unexpectedErrno(err),
             }
         };
-        fl_flags &= ~@as(usize, 1 << @bitOffsetOf(posix.O, "NONBLOCK"));
+        fl_flags |= @as(usize, 1 << @bitOffsetOf(posix.O, "NONBLOCK"));
         while (true) {
             try t.checkCancel();
             switch (posix.errno(posix.system.fcntl(fd, posix.F.SETFL, fl_flags))) {
@@ -1897,7 +1897,7 @@ fn dirOpenFilePosix(
                 else => |err| return posix.unexpectedErrno(err),
             }
         };
-        fl_flags &= ~@as(usize, 1 << @bitOffsetOf(posix.O, "NONBLOCK"));
+        fl_flags |= @as(usize, 1 << @bitOffsetOf(posix.O, "NONBLOCK"));
         while (true) {
             try t.checkCancel();
             switch (posix.errno(posix.system.fcntl(fd, posix.F.SETFL, fl_flags))) {