diff --git a/README.md b/README.md
index 49198a30..113b304c 100644
--- a/README.md
+++ b/README.md
@@ -2,7 +2,7 @@
 
 [![NuGet version (Newtonsoft.Json)](https://img.shields.io/nuget/v/Newtonsoft.Json.svg?style=flat-square)](https://www.nuget.org/packages/Newtonsoft.Json/)
 [![Build status](https://ci.appveyor.com/api/projects/status/h1py293didjv3428/branch/master?svg=true)](https://ci.appveyor.com/project/JamesNewtonKing/newtonsoft-json)
-	
+
 - [Homepage](http://www.newtonsoft.com/json)
 - [Documentation](http://www.newtonsoft.com/json/help)
 - [NuGet Package](https://www.nuget.org/packages/Newtonsoft.Json)
diff --git a/Src/Newtonsoft.Json.Tests/Linq/JObjectTests.cs b/Src/Newtonsoft.Json.Tests/Linq/JObjectTests.cs
index ce5e4e95..04a1de1d 100644
--- a/Src/Newtonsoft.Json.Tests/Linq/JObjectTests.cs
+++ b/Src/Newtonsoft.Json.Tests/Linq/JObjectTests.cs
@@ -293,6 +293,27 @@ namespace Newtonsoft.Json.Tests.Linq
             Assert.AreEqual(false, contains);
         }
 
+        [Test]
+        public void Contains()
+        {
+            JObject o = new JObject();
+            o.Add("PropertyNameValue", new JValue(1));
+            Assert.AreEqual(1, o.Children().Count());
+
+            bool contains = o.ContainsKey("PropertyNameValue");
+            Assert.AreEqual(true, contains);
+
+            contains = o.ContainsKey("does not exist");
+            Assert.AreEqual(false, contains);
+
+            ExceptionAssert.Throws<ArgumentNullException>(() =>
+            {
+                contains = o.ContainsKey(null);
+                Assert.AreEqual(false, contains);
+            }, @"Value cannot be null.
+Parameter name: propertyName");
+        }
+
         [Test]
         public void GenericDictionaryContains()
         {
diff --git a/Src/Newtonsoft.Json/Linq/JObject.cs b/Src/Newtonsoft.Json/Linq/JObject.cs
index 5d9081f9..d1092bbc 100644
--- a/Src/Newtonsoft.Json/Linq/JObject.cs
+++ b/Src/Newtonsoft.Json/Linq/JObject.cs
@@ -541,9 +541,16 @@ namespace Newtonsoft.Json.Linq
             Add(new JProperty(propertyName, value));
         }
 
-        bool IDictionary<string, JToken>.ContainsKey(string key)
+        /// <summary>
+        /// Determines whether the JSON object has the specified property name.
+        /// </summary>
+        /// <param name="propertyName">Name of the property.</param>
+        /// <returns><c>true</c> if the JSON object has the specified property name; otherwise, <c>false</c>.</returns>
+        public bool ContainsKey(string propertyName)
         {
-            return _properties.Contains(key);
+            ValidationUtils.ArgumentNotNull(propertyName, nameof(propertyName));
+
+            return _properties.Contains(propertyName);
         }
 
         ICollection<string> IDictionary<string, JToken>.Keys => _properties.Keys;