diff --git a/lib/std/Io/Threaded.zig b/lib/std/Io/Threaded.zig
index bcbc1ec9cc5351ee540546ccdb72d7151a0ed2f9..eafcfb931b81bbe4a69a6bffd285c448aee8b605 100644
--- a/lib/std/Io/Threaded.zig
+++ b/lib/std/Io/Threaded.zig
@@ -4403,7 +4403,7 @@ fn dirCreateFilePosix(
             }
         };
 
-        fl_flags |= @as(usize, 1 << @bitOffsetOf(posix.O, "NONBLOCK"));
+        fl_flags &= ~@as(usize, 1 << @bitOffsetOf(posix.O, "NONBLOCK"));
 
         const syscall: Syscall = try .start();
         while (true) {
@@ -4999,7 +4999,7 @@ fn dirOpenFilePosix(
             }
         };
 
-        fl_flags |= @as(usize, 1 << @bitOffsetOf(posix.O, "NONBLOCK"));
+        fl_flags &= ~@as(usize, 1 << @bitOffsetOf(posix.O, "NONBLOCK"));
 
         const syscall: Syscall = try .start();
         while (true) {