diff --git a/src/Zio.Tests/TestUPathExtension.cs b/src/Zio.Tests/TestUPathExtension.cs
new file mode 100644
index 0000000..b778875
--- /dev/null
+++ b/src/Zio.Tests/TestUPathExtension.cs
@@ -0,0 +1,29 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Xunit;
+
+namespace Zio.Tests
+{
+    public class TestUPathExtension
+    {
+
+
+        [Theory]
+        [InlineData("/a/b", "a", "b")]
+        [InlineData("/a/b/c", "a", "b/c")]
+        [InlineData("a/b", "a", "b")]
+        [InlineData("a/b/c", "a", "b/c")]
+        [InlineData("", "", "")]
+        [InlineData("/z","z","")]
+
+        public void TestGetFirstDirectory(string path, string expectedFirstDir, string expectedRest)
+        {
+            var pathInfo = new UPath(path);
+            var firstDir = pathInfo.GetFirstDirectory(out var rest);
+            Assert.Equal(expectedFirstDir,firstDir);
+            Assert.Equal(expectedRest,rest);
+        }
+    }
+}
+
diff --git a/src/Zio/UPathExtensions.cs b/src/Zio/UPathExtensions.cs
index 84fbf10..7f0a616 100644
--- a/src/Zio/UPathExtensions.cs
+++ b/src/Zio/UPathExtensions.cs
@@ -88,14 +88,15 @@ public static string GetFirstDirectory(this UPath path, out UPath remainingPath)
 
             string firstDirectory;
             var fullname = path.FullName;
-            var index = fullname.IndexOf(UPath.DirectorySeparator, 1);
+            var offset = path.IsRelative ? 0 : 1;
+            var index = fullname.IndexOf(UPath.DirectorySeparator, offset);
             if (index < 0)
             {
-                firstDirectory = fullname.Substring(1, fullname.Length - 1);
+                firstDirectory = fullname.Substring(offset, fullname.Length - offset);
             }
             else
             {
-                firstDirectory = fullname.Substring(1, index - 1);
+                firstDirectory = fullname.Substring(offset, index - offset);
                 if (index + 1 < fullname.Length)
                 {
                     remainingPath = fullname.Substring(index + 1);
@@ -265,4 +266,4 @@ public static UPath AssertAbsolute(this UPath path, string name = "path")
             return path.FullName;
         }
     }
-}
\ No newline at end of file
+}