diff --git a/src/Renci.SshNet/AuthenticationMethod.cs b/src/Renci.SshNet/AuthenticationMethod.cs
index 51e49b7ad..99a5e102f 100644
--- a/src/Renci.SshNet/AuthenticationMethod.cs
+++ b/src/Renci.SshNet/AuthenticationMethod.cs
@@ -1,7 +1,5 @@
 using System;
 
-using Renci.SshNet.Common;
-
 namespace Renci.SshNet
 {
     /// <summary>
@@ -34,7 +32,7 @@ public abstract class AuthenticationMethod : IAuthenticationMethod
         /// <exception cref="ArgumentException"><paramref name="username"/> is whitespace or <c>null</c>.</exception>
         protected AuthenticationMethod(string username)
         {
-            if (username.IsNullOrWhiteSpace())
+            if (string.IsNullOrWhiteSpace(username))
             {
                 throw new ArgumentException("username");
             }
diff --git a/src/Renci.SshNet/Common/Extensions.cs b/src/Renci.SshNet/Common/Extensions.cs
index d5c454c70..d734ffd8b 100644
--- a/src/Renci.SshNet/Common/Extensions.cs
+++ b/src/Renci.SshNet/Common/Extensions.cs
@@ -15,31 +15,6 @@ namespace Renci.SshNet.Common
     /// </summary>
     internal static partial class Extensions
     {
-        /// <summary>
-        /// Determines whether the specified value is null or white space.
-        /// </summary>
-        /// <param name="value">The value.</param>
-        /// <returns>
-        /// <c>true</c> if <paramref name="value"/> is null or white space; otherwise, <c>false</c>.
-        /// </returns>
-        public static bool IsNullOrWhiteSpace(this string value)
-        {
-            if (string.IsNullOrEmpty(value))
-            {
-                return true;
-            }
-
-            for (var i = 0; i < value.Length; i++)
-            {
-                if (!char.IsWhiteSpace(value[i]))
-                {
-                    return false;
-                }
-            }
-
-            return true;
-        }
-
         internal static byte[] ToArray(this ServiceName serviceName)
         {
             switch (serviceName)
diff --git a/src/Renci.SshNet/ScpClient.cs b/src/Renci.SshNet/ScpClient.cs
index 7269e81c3..177a83bb5 100644
--- a/src/Renci.SshNet/ScpClient.cs
+++ b/src/Renci.SshNet/ScpClient.cs
@@ -243,7 +243,7 @@ public void Upload(Stream source, string path)
         /// <exception cref="SshException">The secure copy execution request was rejected by the server.</exception>
         public void Download(string filename, Stream destination)
         {
-            if (filename.IsNullOrWhiteSpace())
+            if (string.IsNullOrWhiteSpace(filename))
             {
                 throw new ArgumentException(Message);
             }
diff --git a/src/Renci.SshNet/SftpClient.cs b/src/Renci.SshNet/SftpClient.cs
index 9fe19235a..a275413a1 100644
--- a/src/Renci.SshNet/SftpClient.cs
+++ b/src/Renci.SshNet/SftpClient.cs
@@ -326,7 +326,7 @@ public void CreateDirectory(string path)
         {
             CheckDisposed();
 
-            if (path.IsNullOrWhiteSpace())
+            if (string.IsNullOrWhiteSpace(path))
             {
                 throw new ArgumentException(path);
             }
@@ -355,7 +355,7 @@ public void DeleteDirectory(string path)
         {
             CheckDisposed();
 
-            if (path.IsNullOrWhiteSpace())
+            if (string.IsNullOrWhiteSpace(path))
             {
                 throw new ArgumentException("path");
             }
@@ -384,7 +384,7 @@ public void DeleteFile(string path)
         {
             CheckDisposed();
 
-            if (path.IsNullOrWhiteSpace())
+            if (string.IsNullOrWhiteSpace(path))
             {
                 throw new ArgumentException("path");
             }
@@ -415,7 +415,7 @@ public async Task DeleteFileAsync(string path, CancellationToken cancellationTok
         {
             CheckDisposed();
 
-            if (path.IsNullOrWhiteSpace())
+            if (string.IsNullOrWhiteSpace(path))
             {
                 throw new ArgumentException("path");
             }
@@ -542,12 +542,12 @@ public void SymbolicLink(string path, string linkPath)
         {
             CheckDisposed();
 
-            if (path.IsNullOrWhiteSpace())
+            if (string.IsNullOrWhiteSpace(path))
             {
                 throw new ArgumentException("path");
             }
 
-            if (linkPath.IsNullOrWhiteSpace())
+            if (string.IsNullOrWhiteSpace(linkPath))
             {
                 throw new ArgumentException("linkPath");
             }
@@ -753,7 +753,7 @@ public bool Exists(string path)
         {
             CheckDisposed();
 
-            if (path.IsNullOrWhiteSpace())
+            if (string.IsNullOrWhiteSpace(path))
             {
                 throw new ArgumentException("path");
             }
@@ -882,7 +882,7 @@ public IAsyncResult BeginDownloadFile(string path, Stream output, AsyncCallback
         {
             CheckDisposed();
 
-            if (path.IsNullOrWhiteSpace())
+            if (string.IsNullOrWhiteSpace(path))
             {
                 throw new ArgumentException("path");
             }
@@ -1109,7 +1109,7 @@ public IAsyncResult BeginUploadFile(Stream input, string path, bool canOverride,
                 throw new ArgumentNullException(nameof(input));
             }
 
-            if (path.IsNullOrWhiteSpace())
+            if (string.IsNullOrWhiteSpace(path))
             {
                 throw new ArgumentException("path");
             }
@@ -2106,7 +2106,7 @@ public IEnumerable<FileInfo> SynchronizeDirectories(string sourcePath, string de
                 throw new ArgumentNullException(nameof(sourcePath));
             }
 
-            if (destinationPath.IsNullOrWhiteSpace())
+            if (string.IsNullOrWhiteSpace(destinationPath))
             {
                 throw new ArgumentException("destinationPath");
             }
@@ -2135,7 +2135,7 @@ public IAsyncResult BeginSynchronizeDirectories(string sourcePath, string destin
                 throw new ArgumentNullException(nameof(sourcePath));
             }
 
-            if (destinationPath.IsNullOrWhiteSpace())
+            if (string.IsNullOrWhiteSpace(destinationPath))
             {
                 throw new ArgumentException("destDir");
             }
@@ -2340,7 +2340,7 @@ private void InternalDownloadFile(string path, Stream output, SftpDownloadAsyncR
                 throw new ArgumentNullException(nameof(output));
             }
 
-            if (path.IsNullOrWhiteSpace())
+            if (string.IsNullOrWhiteSpace(path))
             {
                 throw new ArgumentException("path");
             }
@@ -2404,7 +2404,7 @@ private void InternalUploadFile(Stream input, string path, Flags flags, SftpUplo
                 throw new ArgumentNullException(nameof(input));
             }
 
-            if (path.IsNullOrWhiteSpace())
+            if (string.IsNullOrWhiteSpace(path))
             {
                 throw new ArgumentException("path");
             }