diff --git a/lib/src/endpoints/player.dart b/lib/src/endpoints/player.dart
index d290cd4..6c99456 100644
--- a/lib/src/endpoints/player.dart
+++ b/lib/src/endpoints/player.dart
@@ -103,11 +103,13 @@ class PlayerEndpoint extends _MeEndpointBase {
       {String? deviceId,
       StartOrResumeOptions? options,
       bool retrievePlaybackState = true}) async {
-    var body = options?.toJson();
-    var json = jsonEncode(body ?? '');
+    final body = options?.toJson();
+    final json = body != null ? jsonEncode(body) : null;
 
     await _api._put(
-        '$_path/play?${_buildQuery({'device_id': deviceId})}', json);
+      '$_path/play?${_buildQuery({'device_id': deviceId})}',
+      json,
+    );
 
     return retrievePlaybackState ? playbackState() : null;
   }
diff --git a/lib/src/spotify_base.dart b/lib/src/spotify_base.dart
index 2f8a26c..cee0db8 100644
--- a/lib/src/spotify_base.dart
+++ b/lib/src/spotify_base.dart
@@ -193,7 +193,7 @@ abstract class SpotifyApiBase {
     return _deleteImpl('$_baseUrl/$path', const {}, body);
   }
 
-  Future<String> _put(String path, [String body = '']) {
+  Future<String> _put(String path, [String? body]) {
     return _putImpl('$_baseUrl/$path', const {}, body);
   }