diff --git a/src/commons/collections/include/pdc_hash_table.h b/src/commons/collections/include/pdc_hash_table.h
index e5c586fda..0780d1722 100644
--- a/src/commons/collections/include/pdc_hash_table.h
+++ b/src/commons/collections/include/pdc_hash_table.h
@@ -49,6 +49,12 @@ CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 extern "C" {
 #endif
 
+#ifdef ENABLE_MULTITHREAD
+#include "mercury_thread_mutex.h"
+
+extern hg_thread_mutex_t hash_table_new_mutex_g;
+#endif
+
 /**
  * A hash table structure.
  */
diff --git a/src/commons/collections/pdc_hash_table.c b/src/commons/collections/pdc_hash_table.c
index efdcc5e62..0332bf68b 100644
--- a/src/commons/collections/pdc_hash_table.c
+++ b/src/commons/collections/pdc_hash_table.c
@@ -32,6 +32,10 @@ CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 #include "alloc-testing.h"
 #endif
 
+#ifdef ENABLE_MULTITHREAD
+hg_thread_mutex_t hash_table_new_mutex_g;
+#endif
+
 struct _HashTableEntry {
     HashTablePair   pair;
     HashTableEntry *next;
diff --git a/src/server/include/pdc_server.h b/src/server/include/pdc_server.h
index a1af90004..2cc69d18e 100644
--- a/src/server/include/pdc_server.h
+++ b/src/server/include/pdc_server.h
@@ -71,7 +71,6 @@ extern int      use_sqlite3_g;
 /*****************************/
 /* Library-private Variables */
 /*****************************/
-hg_thread_mutex_t hash_table_new_mutex_g;
 hg_thread_mutex_t pdc_client_addr_mutex_g;
 hg_thread_mutex_t pdc_metadata_hash_table_mutex_g;
 hg_thread_mutex_t pdc_container_hash_table_mutex_g;