diff --git a/bin/plugins/filter-aaaa.c b/bin/plugins/filter-aaaa.c
index 838fb7aefa..e62dff59af 100644
--- a/bin/plugins/filter-aaaa.c
+++ b/bin/plugins/filter-aaaa.c
@@ -83,6 +83,7 @@ typedef struct filter_instance {
 	 * Memory pool for use with persistent data.
 	 */
 	isc_mempool_t *datapool;
+	isc_mutex_t plock;
 
 	/*
 	 * Hash table associating a client object with its persistent data.
@@ -388,6 +389,8 @@ plugin_register(const char *parameters,
 	 */
 	isc_mempool_setfillcount(inst->datapool, 1024);
 	isc_mempool_setfreemax(inst->datapool, UINT_MAX);
+	isc_mutex_init(&inst->plock);
+	isc_mempool_associatelock(inst->datapool, &inst->plock);
 
 	/*
 	 * Set hook points in the view's hooktable.
@@ -446,6 +449,7 @@ plugin_destroy(void **instp) {
 	}
 	if (inst->datapool != NULL) {
 		isc_mempool_destroy(&inst->datapool);
+		isc_mutex_destroy(&inst->plock);
 	}
 	if (inst->aaaa_acl != NULL) {
 		dns_acl_detach(&inst->aaaa_acl);