diff --git a/lib/system.nim b/lib/system.nim
index 2c12574671..f457078491 100644
--- a/lib/system.nim
+++ b/lib/system.nim
@@ -2985,7 +2985,7 @@ proc locals*(): TObject {.magic: "Locals", noSideEffect.} =
   ##   # -> B is 1
   discard
 
-proc deepCopy*[T](x: T): T {.magic: "DeepCopy", noSideEffect.}
+proc deepCopy*[T](x: T): T {.magic: "DeepCopy", noSideEffect.} = discard
   ## performs a deep copy of `x`. This is also used by the code generator
   ## for the implementation of ``spawn``.