diff --git a/lib/db.js b/lib/db.js
index 9d2f2e52bd..15f7555777 100644
--- a/lib/db.js
+++ b/lib/db.js
@@ -687,6 +687,8 @@ Db.prototype.listCollections = function(filter, options) {
   // Ensure valid readPreference
   if (options.readPreference) {
     options.readPreference = convertReadPreference(options.readPreference);
+  } else {
+    options.readPreference = this.s.readPreference || ReadPreference.primary;
   }
 
   // We have a list collections command