diff --git a/src/Microsoft.AspNetCore.Server.Kestrel/project.json b/src/Microsoft.AspNetCore.Server.Kestrel/project.json
index ff0115f2c4..dd0812020e 100644
--- a/src/Microsoft.AspNetCore.Server.Kestrel/project.json
+++ b/src/Microsoft.AspNetCore.Server.Kestrel/project.json
@@ -28,6 +28,7 @@
   "frameworks": {
     "net451": {
       "frameworkAssemblies": {
+        "System.Runtime": { "type": "build" },
         "System.Threading.Tasks": { "type": "build" }
       }
     },