diff --git a/build/winsign/sign.ps1 b/build/winsign/sign.ps1
index 6cc1f4f86..6d7351f5f 100644
--- a/build/winsign/sign.ps1
+++ b/build/winsign/sign.ps1
@@ -1,6 +1,6 @@
 param(
-    [string]$RunID,
-    [string]$SignIdentity
+    [string][Parameter(Mandatory=$true)]$SignIdentity,
+    [string][Parameter(Mandatory=$true)]$RunID
 )
 
 $ErrorActionPreference = "Stop"