diff --git a/src/Collection.php b/src/Collection.php
index 4c5b22b1c653813bf210c645ffabda3321c1fa3d..b635c85e2af0c1815b495347eb48a7a1d4cdbd9f 100644
--- a/src/Collection.php
+++ b/src/Collection.php
@@ -551,7 +551,7 @@ class Collection
      * @throws InvalidArgumentException for parameter/option parsing errors
      * @throws DriverRuntimeException for other driver errors (e.g. connection errors)
      */
-    public function EstimatedDocumentCount(array $options = [])
+    public function estimatedDocumentCount(array $options = [])
     {
         if ( ! isset($options['readPreference'])) {
             $options['readPreference'] = $this->readPreference;