diff --git a/src/scanner.cc b/src/scanner.cc
index bf7c9e39c4..3214c6f1c7 100644
--- a/src/scanner.cc
+++ b/src/scanner.cc
@@ -312,8 +312,7 @@ Token::Value Scanner::SkipSourceURLComment() {
 void Scanner::TryToParseSourceURLComment() {
   // Magic comments are of the form: //[#@]\s<name>=\s*<value>\s*.* and this
   // function will just return if it cannot parse a magic comment.
-  if (!unicode_cache_->IsWhiteSpace(c0_))
-    return;
+  if (c0_ < 0 || !unicode_cache_->IsWhiteSpace(c0_)) return;
   Advance();
   LiteralBuffer name;
   while (c0_ >= 0 && !unicode_cache_->IsWhiteSpaceOrLineTerminator(c0_) &&
diff --git a/test/mjsunit/regress/regress-crbug-433766.js b/test/mjsunit/regress/regress-crbug-433766.js
new file mode 100644
index 0000000000..fae94837d4
--- /dev/null
+++ b/test/mjsunit/regress/regress-crbug-433766.js
@@ -0,0 +1,16 @@
+// 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.
+
+var filler = "//" + new Array(('@')).join('x');
+
+// Test strict eval in global context.
+eval(
+  "'use strict';" +
+  "var x = 23;" +
+  "var f = function bozo1() {" +
+  "  return x;" +
+  "};" +
+  "f;" +
+  filler
+)();