diff --git a/vm/write_barrier.cpp b/vm/write_barrier.cpp
old mode 100644
new mode 100755
index 4137b0a6eb..0e87434b56
--- a/vm/write_barrier.cpp
+++ b/vm/write_barrier.cpp
@@ -4,4 +4,8 @@ using namespace factor;
 
 cell cards_offset;
 cell decks_offset;
-cell allot_markers_offset;
+
+namespace factor
+{
+        cell allot_markers_offset;
+}
diff --git a/vm/write_barrier.hpp b/vm/write_barrier.hpp
index e656b66a56..eaede538ed 100755
--- a/vm/write_barrier.hpp
+++ b/vm/write_barrier.hpp
@@ -60,7 +60,7 @@ inline static card *deck_to_card(card_deck *d)
 
 #define INVALID_ALLOT_MARKER 0xff
 
-cell allot_markers_offset;
+extern cell allot_markers_offset;
 
 inline static card *addr_to_allot_marker(object *a)
 {