diff --git a/src/util/slab.c b/src/util/slab.c
index 62634034fdc..b0f07e0202d 100644
--- a/src/util/slab.c
+++ b/src/util/slab.c
@@ -257,7 +257,8 @@ void slab_free(struct slab_child_pool *pool, void *ptr)
    }
 
    /* The slow case: migration or an orphaned page. */
-   mtx_lock(&pool->parent->mutex);
+   if (pool->parent)
+      mtx_lock(&pool->parent->mutex);
 
    /* Note: we _must_ re-read elt->owner here because the owning child pool
     * may have been destroyed by another thread in the meantime.
@@ -268,9 +269,11 @@ void slab_free(struct slab_child_pool *pool, void *ptr)
       struct slab_child_pool *owner = (struct slab_child_pool *)owner_int;
       elt->next = owner->migrated;
       owner->migrated = elt;
-      mtx_unlock(&pool->parent->mutex);
+      if (pool->parent)
+         mtx_unlock(&pool->parent->mutex);
    } else {
-      mtx_unlock(&pool->parent->mutex);
+      if (pool->parent)
+         mtx_unlock(&pool->parent->mutex);
 
       slab_free_orphaned(elt);
    }