diff --git a/OPTYap/opt.structs.h b/OPTYap/opt.structs.h
index 838ffc77f..01529925a 100644
--- a/OPTYap/opt.structs.h
+++ b/OPTYap/opt.structs.h
@@ -287,9 +287,11 @@ struct local_signals{
 ** --------------------------- */
 
 struct local_data{
+#if defined(YAPOR) || defined(THREADS)
+  lockvar lock;
+#endif
 #ifdef YAPOR
   /* local data related to or-parallelism */
-  lockvar lock;
   volatile int load;
   choiceptr top_choice_point;
   struct or_frame *top_or_frame;
diff --git a/OPTYap/tab.structs.h b/OPTYap/tab.structs.h
index 0e840f8a4..448a3d0f7 100644
--- a/OPTYap/tab.structs.h
+++ b/OPTYap/tab.structs.h
@@ -54,7 +54,7 @@
 ** ---------------------------- */
 
 typedef struct table_entry {
-#ifdef YAPOR
+#if defined(YAPOR) || defined(THREADS)
   lockvar lock;
 #endif /* YAPOR */
   struct pred_entry *pred_entry;
@@ -187,8 +187,10 @@ typedef struct answer_trie_hash {
 ** ------------------------------ */
 
 typedef struct subgoal_frame {
-#ifdef YAPOR
+#if defined(YAPOR) || defined(THREADS)
   lockvar lock;
+#endif
+#ifdef YAPOR
   int generator_worker;
   struct or_frame *top_or_frame_on_generator_branch;
 #endif /* YAPOR */
@@ -263,8 +265,10 @@ typedef struct subgoal_frame {
 ** --------------------------------- */
 
 typedef struct dependency_frame {
-#ifdef YAPOR
+#if defined(YAPOR) || defined(THREADS)
   lockvar lock;
+#endif
+#ifdef YAPOR
   int leader_dependency_is_on_stack;
   struct or_frame *top_or_frame;
 #ifdef TIMESTAMP_CHECK