diff --git a/lib/Service/AbstractService.php b/lib/Service/AbstractService.php
index abcc13ae2e..a0064ba89e 100644
--- a/lib/Service/AbstractService.php
+++ b/lib/Service/AbstractService.php
@@ -40,14 +40,17 @@ public function getClient()
      *
      * @param null|array $params
      */
-    private static function formatParams($params)
+    public static function formatParams($params)
     {
         if (null === $params) {
             return $params;
         }
+
         $formatted = [];
         foreach ($params as $k => $v) {
-            if (null === $v) {
+            if (is_array($v)) {
+              $formatted[$k] = static::formatParams($v);
+            } else if (null === $v) {
                 $formatted[$k] = '';
             } else {
                 $formatted[$k] = $v;
diff --git a/tests/Stripe/Service/AbstractServiceTest.php b/tests/Stripe/Service/AbstractServiceTest.php
index deee3e3869..059badb0f6 100644
--- a/tests/Stripe/Service/AbstractServiceTest.php
+++ b/tests/Stripe/Service/AbstractServiceTest.php
@@ -57,4 +57,16 @@ public function testRetrieveThrowsIfIdNullIsWhitespace()
 
         $this->service->retrieve(' ');
     }
+
+    public function testFormatParams() {
+      $result = \Stripe\Service\AbstractService::formatParams(["foo" => null]);
+      static::assertTrue($result["foo"] === "");
+      static::assertTrue($result["foo"] !== null);
+
+
+      $result = \Stripe\Service\AbstractService::formatParams(["foo" => ["bar" => null, "baz" => 1]]);
+      static::assertTrue($result["foo"]["bar"] === "");
+      static::assertTrue($result["foo"]["bar"] !== null);
+      static::assertTrue($result["foo"]["baz"] === 1);
+    }
 }