diff --git a/src/main.zig b/src/main.zig
index c0bf8f2395..4de0670d8f 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -304,11 +304,7 @@ fn mainArgs(
         return process.exit(try llvmArMain(arena, args));
     } else if (mem.eql(u8, cmd, "build")) {
         dev.check(.build_command);
-        var thread_safe_arena: std.heap.ThreadSafeAllocator = .{
-            .child_allocator = arena,
-            .io = io,
-        };
-        return cmdBuild(gpa, thread_safe_arena.allocator(), io, cmd_args, environ_map);
+        return cmdBuild(gpa, arena, io, cmd_args, environ_map);
     } else if (mem.eql(u8, cmd, "clang") or
         mem.eql(u8, cmd, "-cc1") or mem.eql(u8, cmd, "-cc1as"))
     {
@@ -4914,7 +4910,6 @@ test sanitizeExampleName {
 
 fn cmdBuild(
     gpa: Allocator,
-    /// Needs a thread-safe arena.
     arena: Allocator,
     io: Io,
     args: []const []const u8,