diff --git a/src/genericmemory.c b/src/genericmemory.c
index f3fa3e2d77320..d98c8302d3573 100644
--- a/src/genericmemory.c
+++ b/src/genericmemory.c
@@ -273,6 +273,7 @@ JL_DLLEXPORT void jl_genericmemory_copyto(jl_genericmemory_t *dest, char* destda
         _Atomic(void*) * dest_p = (_Atomic(void*)*)destdata;
         _Atomic(void*) * src_p = (_Atomic(void*)*)srcdata;
         jl_value_t *owner = jl_genericmemory_owner(dest);
+        mmtk_gc_wb(owner, NULL);
         if (__unlikely(jl_astaggedvalue(owner)->bits.gc == GC_OLD_MARKED)) {
             jl_value_t *src_owner = jl_genericmemory_owner(src);
             ssize_t done = 0;
diff --git a/src/llvm-final-gc-lowering.cpp b/src/llvm-final-gc-lowering.cpp
index f8802a8f62514..401ad983f8c81 100644
--- a/src/llvm-final-gc-lowering.cpp
+++ b/src/llvm-final-gc-lowering.cpp
@@ -418,6 +418,7 @@ bool FinalLowerGC::runOnFunction(Function &F)
             ++it;
 
 #undef LOWER_INTRINSIC
+#undef LOWER_WB_INTRINSIC
         }
     }