diff --git a/src/Microsoft.AspNet.Server.Testing/project.json b/src/Microsoft.AspNet.Server.Testing/project.json
index 77260810ac..44cd34edf5 100644
--- a/src/Microsoft.AspNet.Server.Testing/project.json
+++ b/src/Microsoft.AspNet.Server.Testing/project.json
@@ -23,7 +23,7 @@
         "dnxcore50": {
             "dependencies": {
                 "System.Diagnostics.Process": "4.0.0-beta-*",
-                "System.IO.FileSystem": "4.0.0-*",
+                "System.IO.FileSystem": "4.0.1-beta-*",
                 "System.Net.Http": "4.0.1-beta-*",
                 "System.Net.Primitives": "4.0.11-beta-*",
                 "System.Runtime.Extensions": "4.0.11-beta-*",