diff --git a/lib/system.nim b/lib/system.nim
index 19f5b12804..b53bd58526 100644
--- a/lib/system.nim
+++ b/lib/system.nim
@@ -1459,6 +1459,7 @@ proc isNil*[T: proc | iterator {.closure.}](x: T): bool {.noSideEffect, magic: "
   ## `== nil`.
 
 proc supportsCopyMem(t: typedesc): bool {.magic: "TypeTrait".}
+proc canFormCycles(t: typedesc): bool {.magic: "TypeTrait".}
 
 when defined(nimHasTopDownInference):
   # magic used for seq type inference