diff --git a/BUILD.gn b/BUILD.gn
index 11524ba7c3..0cfa6a7356 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -3816,14 +3816,6 @@ if (v8_use_snapshot && current_toolchain == v8_snapshot_toolchain) {
       ":v8_nosnapshot",
       "//build/win:default_exe_manifest",
     ]
-
-    if (target_os == "fuchsia") {
-      defines = [ "V8_TARGET_OS_FUCHSIA" ]
-    } else if (target_os == "win") {
-      defines = [ "V8_TARGET_OS_WIN" ]
-    } else if (target_os == "chromeos") {
-      defines = [ "V8_TARGET_OS_CHROMEOS" ]
-    }
   }
 }