diff --git a/src/char-predicates.cc b/src/char-predicates.cc
new file mode 100644
index 0000000..ab551d8
--- /dev/null
+++ b/src/char-predicates.cc
@@ -0,0 +1,42 @@
+// Copyright 2011 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.
+
+#include "src/char-predicates.h"
+
+#ifdef V8_I18N_SUPPORT
+#include "unicode/uchar.h"
+#include "unicode/urename.h"
+#endif  // V8_I18N_SUPPORT
+
+namespace v8 {
+namespace internal {
+
+bool SupplementaryPlanes::IsIDStart(uc32 c) {
+  DCHECK(c > 0xFFFF);
+#ifdef V8_I18N_SUPPORT
+  // This only works for code points in the SMPs, since ICU does not exclude
+  // code points with properties 'Pattern_Syntax' or 'Pattern_White_Space'.
+  // Code points in the SMP do not have those properties.
+  return u_isIDStart(c);
+#else
+  // This is incorrect, but if we don't have ICU, use this as fallback.
+  return false;
+#endif  // V8_I18N_SUPPORT
+}
+
+
+bool SupplementaryPlanes::IsIDPart(uc32 c) {
+  DCHECK(c > 0xFFFF);
+#ifdef V8_I18N_SUPPORT
+  // This only works for code points in the SMPs, since ICU does not exclude
+  // code points with properties 'Pattern_Syntax' or 'Pattern_White_Space'.
+  // Code points in the SMP do not have those properties.
+  return u_isIDPart(c);
+#else
+  // This is incorrect, but if we don't have ICU, use this as fallback.
+  return false;
+#endif  // V8_I18N_SUPPORT
+}
+}
+}  // namespace v8::internal