diff --git a/src/mzscheme/src/struct.c b/src/mzscheme/src/struct.c
index f0cea1cedc..d15c8860de 100644
--- a/src/mzscheme/src/struct.c
+++ b/src/mzscheme/src/struct.c
@@ -146,7 +146,7 @@ static Scheme_Object *scheme_checked_proc_property;
 static void register_traversers(void);
 #endif
 
-static Scheme_Bucket_Table *prefab_table;
+static THREAD_LOCAL Scheme_Bucket_Table *prefab_table;
 static Scheme_Object *make_prefab_key(Scheme_Struct_Type *type);
 
 #define cons scheme_make_pair