diff --git a/src/weakmap.js b/src/weakmap.js
index b209776829..15056c7f82 100644
--- a/src/weakmap.js
+++ b/src/weakmap.js
@@ -58,13 +58,36 @@ function WeakMapSet(key, value) {
   return %WeakMapSet(this, key, value);
 }
 
+
+function WeakMapHas(key) {
+  if (!IS_SPEC_OBJECT(key)) {
+    throw %MakeTypeError('invalid_weakmap_key', [this, key]);
+  }
+  return !IS_UNDEFINED(%WeakMapGet(this, key));
+}
+
+
+function WeakMapDelete(key) {
+  if (!IS_SPEC_OBJECT(key)) {
+    throw %MakeTypeError('invalid_weakmap_key', [this, key]);
+  }
+  if (!IS_UNDEFINED(%WeakMapGet(this, key))) {
+    %WeakMapSet(this, key, void 0);
+    return true;
+  } else {
+    return false;
+  }
+}
+
 // -------------------------------------------------------------------
 
 function SetupWeakMap() {
   // Setup the non-enumerable functions on the WeakMap prototype object.
   InstallFunctionsOnHiddenPrototype($WeakMap.prototype, DONT_ENUM, $Array(
     "get", WeakMapGet,
-    "set", WeakMapSet
+    "set", WeakMapSet,
+    "has", WeakMapHas,
+    "delete", WeakMapDelete
   ));
 }
 
diff --git a/test/mjsunit/harmony/weakmaps.js b/test/mjsunit/harmony/weakmaps.js
index 52b022bbd8..d98db10df3 100644
--- a/test/mjsunit/harmony/weakmaps.js
+++ b/test/mjsunit/harmony/weakmaps.js
@@ -32,6 +32,8 @@
 var m = new WeakMap;
 assertDoesNotThrow(function () { m.get(new Object) });
 assertDoesNotThrow(function () { m.set(new Object) });
+assertDoesNotThrow(function () { m.has(new Object) });
+assertDoesNotThrow(function () { m.delete(new Object) });
 
 
 // Test invalid getter and setter calls
@@ -55,6 +57,27 @@ TestMapping(m, new Object, 'the-value');
 TestMapping(m, new Object, new Object);
 
 
+// Test expected querying behavior
+var m = new WeakMap;
+var key = new Object;
+TestMapping(m, key, 'to-be-present');
+assertTrue(m.has(key));
+assertFalse(m.has(new Object));
+TestMapping(m, key, undefined);
+assertFalse(m.has(key));
+assertFalse(m.has(new Object));
+
+
+// Test expected deletion behavior
+var m = new WeakMap;
+var key = new Object;
+TestMapping(m, key, 'to-be-deleted');
+assertTrue(m.delete(key));
+assertFalse(m.delete(key));
+assertFalse(m.delete(new Object));
+assertSame(m.get(key), undefined);
+
+
 // Test GC of map with entry
 var m = new WeakMap;
 var key = new Object;
@@ -112,6 +135,8 @@ var m = new WeakMap;
 assertTrue(m instanceof WeakMap);
 assertTrue(WeakMap.prototype.set instanceof Function)
 assertTrue(WeakMap.prototype.get instanceof Function)
+assertTrue(WeakMap.prototype.has instanceof Function)
+assertTrue(WeakMap.prototype.delete instanceof Function)
 
 
 // Stress Test