diff --git a/lib/std/Io/Threaded.zig b/lib/std/Io/Threaded.zig
index efd994bc42319459dcfa63dda5e3c6faec2ec960..4f4b547743707b78ec63cfd46fd33698988afb20 100644
--- a/lib/std/Io/Threaded.zig
+++ b/lib/std/Io/Threaded.zig
@@ -453,7 +453,7 @@ fn async(
     start: *const fn (context: *const anyopaque, result: *anyopaque) void,
 ) ?*Io.AnyFuture {
     const t: *Threaded = @ptrCast(@alignCast(userdata));
-    if (t.cpu_count == 1) {
+    if (t.cpu_count == 1 or builtin.single_threaded) {
         start(context.ptr, result.ptr);
         return null;
     }