diff --git a/src/builtins/builtins-object.cc b/src/builtins/builtins-object.cc
index 85254d5dcd..eba065e5b3 100644
--- a/src/builtins/builtins-object.cc
+++ b/src/builtins/builtins-object.cc
@@ -48,6 +48,10 @@ void Builtins::Generate_ObjectHasOwnProperty(
                               &return_false, &call_runtime);
 
   assembler.Bind(&keyisindex);
+  // Handle negative keys in the runtime.
+  assembler.GotoIf(
+      assembler.IntPtrLessThan(var_index.value(), assembler.IntPtrConstant(0)),
+      &call_runtime);
   assembler.TryLookupElement(object, map, instance_type, var_index.value(),
                              &return_true, &return_false, &call_runtime);
 
diff --git a/src/code-stub-assembler.cc b/src/code-stub-assembler.cc
index 248d8a80e6..41d3565516 100644
--- a/src/code-stub-assembler.cc
+++ b/src/code-stub-assembler.cc
@@ -5084,6 +5084,9 @@ void CodeStubAssembler::TryLookupElement(Node* object, Node* map,
   }
   Bind(&if_isdictionary);
   {
+    // Negative keys must be converted to property names.
+    GotoIf(IntPtrLessThan(intptr_index, IntPtrConstant(0)), if_bailout);
+
     Variable var_entry(this, MachineType::PointerRepresentation());
     Node* elements = LoadElements(object);
     NumberDictionaryLookup<SeededNumberDictionary>(
diff --git a/test/mjsunit/regress/regress-crbug-673008.js b/test/mjsunit/regress/regress-crbug-673008.js
new file mode 100644
index 0000000000..4e232fa99c
--- /dev/null
+++ b/test/mjsunit/regress/regress-crbug-673008.js
@@ -0,0 +1,23 @@
+// Copyright 2016 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 a = {
+  "33": true,
+  "-1": true
+};
+
+var strkeys = Object.keys(a).map(function(k) { return "" + k });
+var numkeys = Object.keys(a).map(function(k) { return +k });
+var keys = strkeys.concat(numkeys);
+
+keys.forEach(function(k) {
+  assertTrue(a.hasOwnProperty(k),
+             "property not found: " + k + "(" + (typeof k) + ")");
+});
+
+var b = {};
+b.__proto__ = a;
+keys.forEach(function(k) {
+  assertTrue(k in b, "property not found: " + k + "(" + (typeof k) + ")");
+});