diff --git a/src/bio.c b/src/bio.c
index 0662c8c4c..85f681185 100644
--- a/src/bio.c
+++ b/src/bio.c
@@ -266,7 +266,7 @@ void bioKillThreads(void) {
     int err, j;
 
     for (j = 0; j < BIO_NUM_OPS; j++) {
-        if (pthread_cancel(bio_threads[j]) == 0) {
+        if (bio_threads[j] && pthread_cancel(bio_threads[j]) == 0) {
             if ((err = pthread_join(bio_threads[j],NULL)) != 0) {
                 serverLog(LL_WARNING,
                     "Bio thread for job type #%d can be joined: %s",