diff --git a/lib/src/utils/open_id_credentials.dart b/lib/src/utils/open_id_credentials.dart
index 8abaea67..108f3490 100644
--- a/lib/src/utils/open_id_credentials.dart
+++ b/lib/src/utils/open_id_credentials.dart
@@ -2,7 +2,7 @@ class OpenIdCredentials {
   String accessToken;
   String tokenType;
   String matrixServerName;
-  int expiresIn;
+  num expiresIn;
 
   OpenIdCredentials(
       {this.accessToken,
@@ -16,4 +16,13 @@ class OpenIdCredentials {
     matrixServerName = json['matrix_server_name'];
     expiresIn = json['expires_in'];
   }
+
+  Map<String, dynamic> toJson() {
+    final Map<String, dynamic> data = Map<String, dynamic>();
+    data['access_token'] = this.accessToken;
+    data['token_type'] = this.tokenType;
+    data['matrix_server_name'] = this.matrixServerName;
+    data['expires_in'] = this.expiresIn;
+    return data;
+  }
 }