diff --git a/tools/external-reference-check.py b/tools/external-reference-check.py
new file mode 100644
index 0000000..386d4a9
--- /dev/null
+++ b/tools/external-reference-check.py
@@ -0,0 +1,43 @@
+#!/usr/bin/env python
+# Copyright 2014 the V8 project authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import re
+import os
+import sys
+
+DECLARE_FILE = "src/assembler.h"
+REGISTER_FILE = "src/serialize.cc"
+DECLARE_RE = re.compile("\s*static ExternalReference ([^(]+)\(")
+REGISTER_RE = re.compile("\s*Add\(ExternalReference::([^(]+)\(")
+
+WORKSPACE = os.path.abspath(os.path.join(os.path.dirname(sys.argv[0]), ".."))
+
+# Ignore those.
+BLACKLISTED = [
+  "page_flags",
+  "math_exp_constants",
+  "math_exp_log_table",
+  "ForDeoptEntry",
+]
+
+def Find(filename, re):
+  references = []
+  with open(filename, "r") as f:
+    for line in f:
+      match = re.match(line)
+      if match:
+        references.append(match.group(1))
+  return references
+
+def Main():
+  declarations = Find(DECLARE_FILE, DECLARE_RE)
+  registrations = Find(REGISTER_FILE, REGISTER_RE)
+  difference = list(set(declarations) - set(registrations) - set(BLACKLISTED))
+  for reference in difference:
+    print("Declared but not registered: ExternalReference::%s" % reference)
+  return len(difference) > 0
+
+if __name__ == "__main__":
+  sys.exit(Main())