diff --git a/evthread.c b/evthread.c
index 13584175..91fe8a1c 100644
--- a/evthread.c
+++ b/evthread.c
@@ -85,7 +85,12 @@ evthread_set_lock_callbacks(const struct evthread_lock_callbacks *cbs)
 	}
 	if (target->alloc) {
 		/* Uh oh; we already had locking callbacks set up.*/
-		if (!memcmp(target, cbs, sizeof(_evthread_lock_fns))) {
+		if (target->lock_api_version == cbs->lock_api_version &&
+			target->supported_locktypes == cbs->supported_locktypes &&
+			target->alloc == cbs->alloc &&
+			target->free == cbs->free &&
+			target->lock == cbs->lock &&
+			target->unlock == cbs->unlock) {
 			/* no change -- allow this. */
 			return 0;
 		}
@@ -118,7 +123,11 @@ evthread_set_condition_callbacks(const struct evthread_condition_callbacks *cbs)
 	}
 	if (target->alloc_condition) {
 		/* Uh oh; we already had condition callbacks set up.*/
-		if (!memcmp(target, cbs, sizeof(_evthread_cond_fns))) {
+		if (target->condition_api_version == cbs->condition_api_version &&
+			target->alloc_condition == cbs->alloc_condition &&
+			target->free_condition == cbs->free_condition &&
+			target->signal_condition == cbs->signal_condition &&
+			target->wait_condition == cbs->wait_condition) {
 			/* no change -- allow this. */
 			return 0;
 		}