diff --git a/README.md b/README.md
index b502b2d..7303642 100644
--- a/README.md
+++ b/README.md
@@ -19,14 +19,23 @@ Returns whether two objects are equal.
 Returns true if the given object has no properties and false otherwise.  This
 is O(1) (unlike `Object.keys(obj).length === 0`, which is O(N)).
 
+### hasKey(obj, key)
+
+Returns true if the given object has an enumerable, non-inherited property
+called `key`.  [For information on enumerability and ownership of properties, see
+the MDN
+documentation.](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Enumerability_and_ownership_of_properties)
 
 ### forEachKey(obj, callback)
 
-Like Array.forEach, but iterates properties of an object rather than elements
-of an array.  Equivalent to:
+Like Array.forEach, but iterates enumerable, owned properties of an object
+rather than elements of an array.  Equivalent to:
 
-    for (var key in obj)
-            callback(key, obj[key]);
+    for (var key in obj) {
+            if (Object.prototype.hasOwnProperty.call(obj, key)) {
+                    callback(key, obj[key]);
+            }
+    }
 
 
 ### flattenObject(obj, depth)
diff --git a/lib/jsprim.js b/lib/jsprim.js
index 5ee4688..26c3ba1 100644
--- a/lib/jsprim.js
+++ b/lib/jsprim.js
@@ -15,6 +15,7 @@ var mod_jsonschema = require('json-schema');
 exports.deepCopy = deepCopy;
 exports.deepEqual = deepEqual;
 exports.isEmpty = isEmpty;
+exports.hasKey = hasKey;
 exports.forEachKey = forEachKey;
 exports.pluck = pluck;
 exports.flattenObject = flattenObject;
@@ -122,10 +123,19 @@ function isEmpty(obj)
 	return (true);
 }
 
+function hasKey(obj, key)
+{
+	mod_assert.equal(typeof (key), 'string');
+	return (Object.prototype.hasOwnProperty.call(obj, key));
+}
+
 function forEachKey(obj, callback)
 {
-	for (var key in obj)
-		callback(key, obj[key]);
+	for (var key in obj) {
+		if (hasKey(obj, key)) {
+			callback(key, obj[key]);
+		}
+	}
 }
 
 function pluck(obj, key)
diff --git a/test/basic.js b/test/basic.js
index e64c4fc..92df8f1 100644
--- a/test/basic.js
+++ b/test/basic.js
@@ -60,6 +60,24 @@ mod_assert.ok(!jsprim.deepEqual(NaN, NaN));
 mod_assert.ok(jsprim.isEmpty({}));
 mod_assert.ok(!jsprim.isEmpty({ 'foo': 'bar' }));
 
+/* hasKey */
+mod_assert.ok(jsprim.hasKey(obj, 'family'));
+mod_assert.ok(jsprim.hasKey(obj, 'children'));
+mod_assert.ok(jsprim.hasKey(obj, 'home'));
+mod_assert.ok(jsprim.hasKey(obj, 'income'));
+mod_assert.ok(jsprim.hasKey(obj, 'dignity'));
+mod_assert.ok(jsprim.hasKey(obj, 'nhomes'));
+mod_assert.ok(obj.hasOwnProperty);
+mod_assert.ok(!jsprim.hasKey(obj, 'hasOwnProperty'));
+copy = Object.create(obj);
+copy.aprop = 'avalue';
+mod_assert.ok(jsprim.hasKey(copy, 'aprop'));
+mod_assert.equal(copy.nhomes, 1);
+mod_assert.ok(!jsprim.hasKey(copy, 'nhomes'));
+copy.hasOwnProperty = null;
+mod_assert.ok(jsprim.hasKey(copy, 'aprop'));
+mod_assert.ok(!jsprim.hasKey(copy, 'nhomes'));
+
 /* forEachKey */
 var keys = [];
 jsprim.forEachKey(obj, function (key, val) {
@@ -70,6 +88,25 @@ keys.sort();
 mod_assert.deepEqual(keys,
     [ 'children', 'dignity', 'family', 'home', 'income', 'nhomes' ]);
 
+/*
+ * forEachKey skips non-own properties and works even on objects with a
+ * hasOwnProperty key overridden.
+ */
+copy = jsprim.deepCopy(obj);
+Object.prototype.aprop = 'avalue';
+mod_assert.equal(copy.aprop, 'avalue');
+copy.hasOwnProperty = null;
+keys = [];
+jsprim.forEachKey(copy, function (key, val) {
+	mod_assert.deepEqual(copy[key], val);
+	keys.push(key);
+});
+keys.sort();
+mod_assert.deepEqual(keys, [ 'children', 'dignity', 'family',
+    'hasOwnProperty', 'home', 'income', 'nhomes' ]);
+delete (Object.prototype.aprop);
+
+
 /* startsWith */
 mod_assert.ok(jsprim.startsWith('foobar', 'f'));
 mod_assert.ok(jsprim.startsWith('foobar', 'foo'));