diff --git a/mozilla/lib/mac/NSStdLib/NSStdLib.exp b/mozilla/lib/mac/NSStdLib/NSStdLib.exp
index f6f22b2cd55..3b2498fe9f8 100644
--- a/mozilla/lib/mac/NSStdLib/NSStdLib.exp
+++ b/mozilla/lib/mac/NSStdLib/NSStdLib.exp
@@ -123,6 +123,7 @@ GC_stderr
 GC_address_to_source
 GC_malloc_atomic
 GC_trace_object
+GC_mark_object
 MWUnmangle
 # GetCatInfoNoName
 # GetDInfo