diff --git a/build.sc b/build.sc
index c16284069fa..34d4e4acfff 100755
--- a/build.sc
+++ b/build.sc
@@ -710,7 +710,7 @@ def assembly = T{
     "-Djna.nosys=true"
   )
   val shellArgs = Seq("-DMILL_CLASSPATH=$0") ++ commonArgs
-  val cmdArgs = Seq("-DMILL_CLASSPATH=%0") ++ commonArgs
+  val cmdArgs = Seq(""""-DMILL_CLASSPATH=%~dpnx0"""") ++ commonArgs
   os.move(
     createAssembly(
       devRunClasspath,