diff --git a/app/src/main/java/org/ntlab/acanthus_client/resources/accounts/WorkRest.java b/app/src/main/java/org/ntlab/acanthus_client/resources/accounts/WorkRest.java
index 6f399ed..e0d57e4 100644
--- a/app/src/main/java/org/ntlab/acanthus_client/resources/accounts/WorkRest.java
+++ b/app/src/main/java/org/ntlab/acanthus_client/resources/accounts/WorkRest.java
@@ -34,6 +34,7 @@
     );
     //-----------------------------------------------------------------
     // 作品への参加を許可する
+    @FormUrlEncoded
     @PUT("accounts/{uid}/work")
     Call<Work> updateWork(
             @Path("uid")String invitedUid,