diff --git a/src/Serve.php b/src/Serve.php
index 6190b4b..bbd10fc 100644
--- a/src/Serve.php
+++ b/src/Serve.php
@@ -112,7 +112,7 @@ public static function serve($options)
 
             if (isset($_POST['options'])) {
                 // Merge in options in $_POST, overwriting the webp-convert options in config
-                $convertOptionsInPost = (array) json_decode($_POST['options']);
+                $convertOptionsInPost = (array) json_decode($_POST['options'], true);
                 $convertOptions = array_merge($options['webp-convert'], $convertOptionsInPost);
             } else {
                 $convertOptions = $options['webp-convert'];