diff --git a/lib/std/Io/Threaded.zig b/lib/std/Io/Threaded.zig
index b8deda5845..3f47272c12 100644
--- a/lib/std/Io/Threaded.zig
+++ b/lib/std/Io/Threaded.zig
@@ -4704,7 +4704,7 @@ fn dirCreateFileAtomic(
                     try syscall.checkCancel();
                     continue;
                 },
-                .ISDIR, .NOENT => {
+                .ISDIR, .NOENT, .OPNOTSUPP => {
                     // Ambiguous error code. It might mean the file system
                     // does not support O_TMPFILE. Therefore, we must fall
                     // back to not using O_TMPFILE.
diff --git a/lib/std/Io/Uring.zig b/lib/std/Io/Uring.zig
index 69a8a28aae..c3330463db 100644
--- a/lib/std/Io/Uring.zig
+++ b/lib/std/Io/Uring.zig
@@ -593,7 +593,10 @@ const CachedFd = struct {
                     @atomicStore(Once, &cached_fd.once, .uninitialized, .monotonic);
                     futexWake(ev, @ptrCast(&cached_fd.once), 1);
                 }
-                const fd = try ev.openat(cancel_region, linux.AT.FDCWD, path, flags, 0);
+                const fd = ev.openat(cancel_region, linux.AT.FDCWD, path, flags, 0) catch |err| switch (err) {
+                    error.OperationUnsupported => return error.Unexpected, // TMPFILE unset.
+                    else => |e| return e,
+                };
                 @atomicStore(Once, &cached_fd.once, .fromFd(fd), .monotonic);
                 futexWake(ev, @ptrCast(&cached_fd.once), std.math.maxInt(u32));
                 return fd;
@@ -2722,12 +2725,10 @@ fn dirOpenDir(
             error.WouldBlock => return errnoBug(.AGAIN),
             error.FileTooBig => return errnoBug(.FBIG),
             error.NoSpaceLeft => return errnoBug(.NOSPC),
-            error.DeviceBusy => return errnoBug(.BUSY), // O_EXCL not passed
+            error.DeviceBusy => return errnoBug(.BUSY), // EXCL unset.
             error.FileBusy => return errnoBug(.TXTBSY),
             error.PathAlreadyExists => return errnoBug(.EXIST), // Not creating.
-            error.PipeBusy => return error.Unexpected, // Not opening a pipe.
-            error.AntivirusInterference => unreachable, // Windows-only
-            error.FileLocksUnsupported => return errnoBug(.OPNOTSUPP), // Not asking for locks.
+            error.OperationUnsupported => return errnoBug(.OPNOTSUPP), // No TMPFILE, no locks.
             else => |e| return e,
         },
     };
@@ -2810,13 +2811,16 @@ fn dirCreateFile(
 
     var maybe_sync: CancelRegion.Sync.Maybe = .{ .cancel_region = .init() };
     defer maybe_sync.deinit(ev);
-    const fd = try ev.openat(&maybe_sync.cancel_region, dir.handle, sub_path_posix, .{
+    const fd = ev.openat(&maybe_sync.cancel_region, dir.handle, sub_path_posix, .{
         .ACCMODE = if (flags.read) .RDWR else .WRONLY,
         .CREAT = true,
         .TRUNC = flags.truncate,
         .EXCL = flags.exclusive,
         .CLOEXEC = true,
-    }, flags.permissions.toMode());
+    }, flags.permissions.toMode()) catch |err| switch (err) {
+        error.OperationUnsupported => return error.Unexpected, // TMPFILE unset.
+        else => |e| return e,
+    };
     errdefer ev.closeAsync(fd);
 
     switch (flags.lock) {
@@ -2892,7 +2896,7 @@ fn dirCreateFileAtomic(
                     flags,
                     options.permissions.toMode(),
                 ) catch |err| switch (err) {
-                    error.IsDir, error.FileNotFound => {
+                    error.IsDir, error.FileNotFound, error.OperationUnsupported => {
                         // Ambiguous error code. It might mean the file system
                         // does not support O_TMPFILE. Therefore, we must fall
                         // back to not using O_TMPFILE.
@@ -2901,9 +2905,6 @@ fn dirCreateFileAtomic(
                     error.FileTooBig => return errnoBug(.FBIG),
                     error.DeviceBusy => return errnoBug(.BUSY), // O_EXCL not passed
                     error.PathAlreadyExists => return errnoBug(.EXIST), // Not creating.
-                    error.PipeBusy => return error.Unexpected, // Not opening a pipe.
-                    error.AntivirusInterference => unreachable, // Windows-only
-                    error.FileLocksUnsupported => return errnoBug(.OPNOTSUPP), // Not asking for locks.
                     else => |e| return e,
                 },
                 .flags = .{ .nonblocking = false },
@@ -2994,7 +2995,7 @@ fn dirOpenFile(
 
     var maybe_sync: CancelRegion.Sync.Maybe = .{ .cancel_region = .init() };
     defer maybe_sync.deinit(ev);
-    const fd = try ev.openat(&maybe_sync.cancel_region, dir.handle, sub_path_posix, .{
+    const fd = ev.openat(&maybe_sync.cancel_region, dir.handle, sub_path_posix, .{
         .ACCMODE = switch (flags.mode) {
             .read_only => .RDONLY,
             .write_only => .WRONLY,
@@ -3004,7 +3005,10 @@ fn dirOpenFile(
         .NOFOLLOW = !flags.follow_symlinks,
         .CLOEXEC = true,
         .PATH = flags.path_only,
-    }, 0);
+    }, 0) catch |err| switch (err) {
+        error.OperationUnsupported => return error.Unexpected, // TMPFILE unset.
+        else => |e| return e,
+    };
     errdefer ev.closeAsync(fd);
 
     if (!flags.allow_directory) {
@@ -3149,7 +3153,7 @@ fn dirRealPathFile(
         .PATH = true,
     }, 0) catch |err| switch (err) {
         error.WouldBlock => return errnoBug(.AGAIN),
-        error.FileLocksUnsupported => return errnoBug(.OPNOTSUPP), // Not asking for locks.
+        error.OperationUnsupported => return errnoBug(.OPNOTSUPP), // Not asking for locks.
         else => |e| return e,
     };
     defer ev.closeAsync(fd);
@@ -5616,7 +5620,7 @@ fn openat(
     path: [*:0]const u8,
     flags: linux.O,
     mode: linux.mode_t,
-) File.OpenError!fd_t {
+) !fd_t {
     var mut_flags = flags;
     if (@hasField(linux.O, "LARGEFILE")) mut_flags.LARGEFILE = true;
     while (true) {
@@ -5662,7 +5666,9 @@ fn openat(
             .PERM => return error.PermissionDenied,
             .EXIST => return error.PathAlreadyExists,
             .BUSY => return error.DeviceBusy,
-            .OPNOTSUPP => return error.FileLocksUnsupported,
+            // This can be triggered by file locking and TMPFILE, but those
+            // flags are mutually exclusive.
+            .OPNOTSUPP => return error.OperationUnsupported,
             .AGAIN => return error.WouldBlock,
             .TXTBSY => return error.FileBusy,
             .NXIO => return error.NoDevice,