diff --git a/ospec/ospec.js b/ospec/ospec.js
index 24495b87..56111b66 100644
--- a/ospec/ospec.js
+++ b/ospec/ospec.js
@@ -135,7 +135,7 @@ module.exports = new function init() {
 			var aIsArgs = isArguments(a), bIsArgs = isArguments(b)
 			if (a.constructor === Object && b.constructor === Object && !aIsArgs && !bIsArgs) {
 				for (var i in a) {
-					if (!deepEqual(a[i], b[i])) return false
+					if ((!(i in b)) || !deepEqual(a[i], b[i])) return false
 				}
 				for (var i in b) {
 					if (!(i in a)) return false
@@ -145,9 +145,8 @@ module.exports = new function init() {
 			if (a.length === b.length && (a instanceof Array && b instanceof Array || aIsArgs && bIsArgs)) {
 				var aKeys = Object.getOwnPropertyNames(a), bKeys = Object.getOwnPropertyNames(b)
 				if (aKeys.length !== bKeys.length) return false
-				var larger = aKeys.length < bKeys.length ? bKeys : aKeys
-				for (var i = 0; i < larger.length; i++) {
-					if (!deepEqual(a[larger[i]], b[larger[i]])) return false
+				for (var i = 0; i < aKeys.length; i++) {
+					if (!b.hasOwnProperty(aKeys[i]) || !deepEqual(a[aKeys[i]], b[aKeys[i]])) return false
 				}
 				return true
 			}
diff --git a/ospec/tests/test-ospec.js b/ospec/tests/test-ospec.js
index a1433d26..b3878f7a 100644
--- a/ospec/tests/test-ospec.js
+++ b/ospec/tests/test-ospec.js
@@ -36,7 +36,21 @@ o.spec("ospec", function() {
 			o(a).notEquals(2)
 			o({a: [1, 2], b: 3}).deepEquals({a: [1, 2], b: 3})
 			o([{a: 1, b: 2}, {c: 3}]).deepEquals([{a: 1, b: 2}, {c: 3}])
+
+			var undef1 = {undef: void 0}
+			var undef2 = {UNDEF: void 0}
+
+			o(undef1).notDeepEquals(undef2)
+			o(undef1).notDeepEquals({})
+			o({}).notDeepEquals(undef1)
 			
+			var sparse1 = [void 1, void 2, void 3]
+			delete sparse1[0]
+			var sparse2 = [void 1, void 2, void 3]
+			delete sparse2[1]
+
+			o(sparse1).notDeepEquals(sparse2)
+
 			var monkeypatch1 = [1, 2]
 			monkeypatch1.field = 3
 			var monkeypatch2 = [1, 2]
@@ -45,6 +59,14 @@ o.spec("ospec", function() {
 			o(monkeypatch1).notDeepEquals([1, 2])
 			o(monkeypatch1).notDeepEquals(monkeypatch2)
 
+			monkeypatch2.field = 3
+			o(monkeypatch1).deepEquals(monkeypatch2)
+
+			monkeypatch1.undef = undefined
+			monkeypatch2.UNDEF = undefined
+
+			o(monkeypatch1).notDeepEquals(monkeypatch2)
+
 			var values = ["a", "", 1, 0, true, false, null, undefined, Date(0), ["a"], [], function() {return arguments}.call(), new Uint8Array(), {a: 1}, {}]
 			for (var i = 0; i < values.length; i++) {
 				for (var j = 0; j < values.length; j++) {