diff --git a/src/Commands/SubTree.cs b/src/Commands/SubTree.cs
index 6c963d09..62f632fe 100644
--- a/src/Commands/SubTree.cs
+++ b/src/Commands/SubTree.cs
@@ -1,4 +1,5 @@
 using System;
+using System.IO;
 
 namespace SourceGit.Commands {
     /// <summary>
@@ -17,6 +18,9 @@ namespace SourceGit.Commands {
         }
 
         public bool Add(string prefix, string source, string revision, bool squash, Action<string> onProgress) {
+            var path = Path.Combine(Cwd, prefix);
+            if (Directory.Exists(path)) return true;
+
             handler = onProgress;
             Args = $"subtree add --prefix=\"{prefix}\" {source} {revision}";
             if (squash) Args += " --squash";