diff --git a/OPTYap/opt.config.h b/OPTYap/opt.config.h
index 4e28b927c..cc0664925 100644
--- a/OPTYap/opt.config.h
+++ b/OPTYap/opt.config.h
@@ -20,7 +20,9 @@
 /******************************************************************************************
 **      use shared pages memory alloc scheme for OPTYap data structures? (optional)      **
 ******************************************************************************************/
-/* #define USE_PAGES_MALLOC 1 */
+#ifdef THREADS
+#define USE_PAGES_MALLOC 1
+#endif
 
 
 
diff --git a/OPTYap/opt.structs.h b/OPTYap/opt.structs.h
index 9c5fc8719..471f067ab 100644
--- a/OPTYap/opt.structs.h
+++ b/OPTYap/opt.structs.h
@@ -79,7 +79,7 @@ typedef struct page_header {
 
 struct pages {
 #ifdef USE_PAGES_MALLOC
-#ifdef YAPOR
+#if defined(YAPOR) || defined(THREADS)
   lockvar lock;
 #endif /* YAPOR */
   int structs_per_page;