diff --git a/src/Microsoft.AspNet.WebUtilities/project.json b/src/Microsoft.AspNet.WebUtilities/project.json
index b3fb9c1ef6..5837682b5e 100644
--- a/src/Microsoft.AspNet.WebUtilities/project.json
+++ b/src/Microsoft.AspNet.WebUtilities/project.json
@@ -13,6 +13,7 @@
                 "System.Diagnostics.Debug": "4.0.10-beta-*",
                 "System.IO": "4.0.10-beta-*",
                 "System.IO.FileSystem": "4.0.0-beta-*",
+                "System.IO.FileSystem.Primitives": "4.0.0-beta-*",
                 "System.Runtime": "4.0.20-beta-*",
                 "System.Runtime.Extensions": "4.0.10-beta-*"
             }