diff --git a/lib/compiler/build_runner.zig b/lib/compiler/build_runner.zig
index 1a019c80d9..31985f3e3d 100644
--- a/lib/compiler/build_runner.zig
+++ b/lib/compiler/build_runner.zig
@@ -415,7 +415,7 @@ pub fn main() !void {
         else => return err,
     };
 
-    var w = if (watch) try Watch.init() else undefined;
+    var w: Watch = if (watch and Watch.have_impl) try Watch.init() else undefined;
 
     try run.thread_pool.init(thread_pool_options);
     defer run.thread_pool.deinit();
diff --git a/lib/std/Build/Watch.zig b/lib/std/Build/Watch.zig
index 13540a2b36..bae3af1f63 100644
--- a/lib/std/Build/Watch.zig
+++ b/lib/std/Build/Watch.zig
@@ -600,7 +600,7 @@ const Os = switch (builtin.os.tag) {
             };
         }
     },
-    .dragonfly, .freebsd, .netbsd, .openbsd, .ios, .macos, .tvos, .visionos, .watchos, .haiku => struct {
+    .dragonfly, .freebsd, .netbsd, .openbsd, .ios, .macos, .tvos, .visionos, .watchos => struct {
         const posix = std.posix;
 
         kq_fd: i32,