diff --git a/BUILD.gn b/BUILD.gn
index 9c8cf50b45..228f50ce6f 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -575,10 +575,12 @@ disabled_external_v8_defines = external_v8_defines - enabled_external_v8_defines
 config("v8_header_features") {
   visibility = [ ":*" ]
 
+  # TODO(v8:11292): Set defines as well as including the header. This is a short
+  # term change to check that the header doesn't get stale and fail to get
+  # updated.
+  defines = enabled_external_v8_defines
   if (v8_generate_external_defines_header) {
-    defines = [ "V8_GN_HEADER" ]
-  } else {
-    defines = enabled_external_v8_defines
+    defines += [ "V8_GN_HEADER" ]
   }
 }
 
@@ -608,10 +610,12 @@ disabled_external_cppgc_defines =
 config("cppgc_header_features") {
   visibility = [ ":*" ]
 
+  # TODO(v8:11292): Set defines as well as including the header. This is a short
+  # term change to check that the header doesn't get stale and fail to get
+  # updated.
+  defines = enabled_external_cppgc_defines
   if (v8_generate_external_defines_header) {
-    defines = [ "V8_GN_HEADER" ]
-  } else {
-    defines = enabled_external_cppgc_defines
+    defines += [ "V8_GN_HEADER" ]
   }
 }