diff --git a/test/built-ins/Proxy/defineProperty/trap-is-missing-target-is-proxy.js b/test/built-ins/Proxy/defineProperty/trap-is-missing-target-is-proxy.js
new file mode 100644
index 0000000000..3a5946b1dc
--- /dev/null
+++ b/test/built-ins/Proxy/defineProperty/trap-is-missing-target-is-proxy.js
@@ -0,0 +1,48 @@
+// Copyright (C) 2020 Alexey Shvayka. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-proxy-object-internal-methods-and-internal-slots-defineownproperty-p-desc
+description: >
+  If "defineProperty" trap is null or undefined, [[DefineOwnProperty]] call
+  is properly forwarded to [[ProxyTarget]] (which is also a Proxy object).
+info: |
+  [[DefineOwnProperty]] (P, Desc)
+
+  [...]
+  5. Let target be O.[[ProxyTarget]].
+  6. Let trap be ? GetMethod(handler, "defineProperty").
+  7. If trap is undefined, then
+    a. Return ? target.[[DefineOwnProperty]](P, Desc).
+features: [Proxy, Reflect]
+---*/
+
+var string = new String("str");
+var stringTarget = new Proxy(string, {});
+var stringProxy = new Proxy(stringTarget, {});
+
+assert(Reflect.defineProperty(stringProxy, "4", {value: 4}));
+assert.sameValue(string[4], 4);
+
+assert.throws(TypeError, function() {
+  Object.defineProperty(stringProxy, "0", {
+    value: "x",
+  });
+});
+
+Object.preventExtensions(string);
+assert(!Reflect.defineProperty(stringProxy, "foo", {value: 5}));
+
+
+var func = function() {};
+var funcTarget = new Proxy(func, {});
+var funcProxy = new Proxy(funcTarget, {});
+
+Object.defineProperty(funcProxy, "name", {value: "foo"});
+assert.sameValue(func.name, "foo");
+
+assert.throws(TypeError, function() {
+  Object.defineProperty(funcProxy, "prototype", {
+    set: function(_value) {},
+  });
+});
diff --git a/test/built-ins/Proxy/defineProperty/trap-is-null-target-is-proxy.js b/test/built-ins/Proxy/defineProperty/trap-is-null-target-is-proxy.js
new file mode 100644
index 0000000000..b7351f85c3
--- /dev/null
+++ b/test/built-ins/Proxy/defineProperty/trap-is-null-target-is-proxy.js
@@ -0,0 +1,57 @@
+// Copyright (C) 2020 Alexey Shvayka. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-proxy-object-internal-methods-and-internal-slots-defineownproperty-p-desc
+description: >
+  If "defineProperty" trap is null or undefined, [[DefineOwnProperty]] call
+  is properly forwarded to [[ProxyTarget]] (which is also a Proxy object).
+info: |
+  [[DefineOwnProperty]] (P, Desc)
+
+  [...]
+  5. Let target be O.[[ProxyTarget]].
+  6. Let trap be ? GetMethod(handler, "defineProperty").
+  7. If trap is undefined, then
+    a. Return ? target.[[DefineOwnProperty]](P, Desc).
+features: [Proxy, Reflect]
+includes: [propertyHelper.js]
+---*/
+
+var plainObject = Object.create(null);
+Object.defineProperty(plainObject, "foo", {
+  configurable: false,
+});
+
+var plainObjectTarget = new Proxy(plainObject, {});
+var plainObjectProxy = new Proxy(plainObjectTarget, {
+  defineProperty: null,
+});
+
+assert.throws(TypeError, function() {
+  Object.defineProperty(plainObjectProxy, "foo", {
+    configurable: true,
+  });
+});
+
+Object.defineProperty(plainObjectProxy, "bar", {
+  get: function() {
+    return 2;
+  },
+});
+assert.sameValue(plainObject.bar, 2);
+
+
+var regExp = /(?:)/g;
+var regExpTarget = new Proxy(regExp, {});
+var regExpProxy = new Proxy(regExpTarget, {
+  defineProperty: null,
+});
+
+assert(
+  Reflect.defineProperty(regExpProxy, "lastIndex", {
+    writable: false,
+  })
+);
+
+verifyNotWritable(regExp, "lastIndex");
diff --git a/test/built-ins/Proxy/defineProperty/trap-is-undefined-target-is-proxy.js b/test/built-ins/Proxy/defineProperty/trap-is-undefined-target-is-proxy.js
new file mode 100644
index 0000000000..559197fe22
--- /dev/null
+++ b/test/built-ins/Proxy/defineProperty/trap-is-undefined-target-is-proxy.js
@@ -0,0 +1,55 @@
+// Copyright (C) 2020 Alexey Shvayka. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-proxy-object-internal-methods-and-internal-slots-defineownproperty-p-desc
+description: >
+  If "defineProperty" trap is null or undefined, [[DefineOwnProperty]] call
+  is properly forwarded to [[ProxyTarget]] (which is also a Proxy object).
+info: |
+  [[DefineOwnProperty]] (P, Desc)
+
+  [...]
+  5. Let target be O.[[ProxyTarget]].
+  6. Let trap be ? GetMethod(handler, "defineProperty").
+  7. If trap is undefined, then
+    a. Return ? target.[[DefineOwnProperty]](P, Desc).
+features: [Proxy, Reflect]
+includes: [compareArray.js]
+---*/
+
+var array = [];
+var arrayTarget = new Proxy(array, {});
+var arrayProxy = new Proxy(arrayTarget, {
+  defineProperty: undefined,
+});
+
+Object.defineProperty(arrayProxy, "0", {value: 1});
+assert.compareArray(array, [1]);
+
+assert.throws(TypeError, function() {
+  Object.defineProperty(arrayProxy, "length", {
+    get: function() {},
+  });
+});
+
+
+var trapCalls = 0;
+var target = new Proxy({}, {
+  defineProperty: function(_target, key) {
+    trapCalls++;
+    return key === "foo";
+  },
+});
+
+var proxy = new Proxy(target, {
+  defineProperty: undefined,
+});
+
+assert(Reflect.defineProperty(proxy, "foo", {}));
+assert.sameValue(trapCalls, 1);
+
+assert.throws(TypeError, function() {
+  Object.defineProperty(proxy, "bar", {});
+});
+assert.sameValue(trapCalls, 2);