diff --git a/src/main/java/com/authlete/jaxrs/ResponseUtil.java b/src/main/java/com/authlete/jaxrs/ResponseUtil.java
index c7a1b9d7..277743c4 100644
--- a/src/main/java/com/authlete/jaxrs/ResponseUtil.java
+++ b/src/main/java/com/authlete/jaxrs/ResponseUtil.java
@@ -32,10 +32,10 @@
 class ResponseUtil
 {
     /**
-     * {@code "application/json;charset=UTF-8"}
+     * {@code "application/json"}
      */
     private static final MediaType MEDIA_TYPE_JSON =
-            MediaType.APPLICATION_JSON_TYPE.withCharset("UTF-8");
+            MediaType.APPLICATION_JSON_TYPE;
 
 
     /**
diff --git a/src/main/java/com/authlete/jaxrs/api/AuthleteApiJaxrsImpl.java b/src/main/java/com/authlete/jaxrs/api/AuthleteApiJaxrsImpl.java
index 09a492e4..157f2be9 100644
--- a/src/main/java/com/authlete/jaxrs/api/AuthleteApiJaxrsImpl.java
+++ b/src/main/java/com/authlete/jaxrs/api/AuthleteApiJaxrsImpl.java
@@ -57,8 +57,8 @@
 
 public abstract class AuthleteApiJaxrsImpl implements AuthleteApi
 {
-    // "application/json;charset=UTF-8"
-    private static final MediaType JSON_UTF8_TYPE = APPLICATION_JSON_TYPE.withCharset("UTF-8");
+    // "application/json"
+    private static final MediaType JSON_UTF8_TYPE = APPLICATION_JSON_TYPE;
 
 
     protected interface AuthleteApiCall<TResponse>