diff --git a/src/main/scala/com/github/dakatsuka/akka/http/oauth2/client/strategy/AuthorizationCodeStrategy.scala b/src/main/scala/com/github/dakatsuka/akka/http/oauth2/client/strategy/AuthorizationCodeStrategy.scala
index e62f608..620df97 100644
--- a/src/main/scala/com/github/dakatsuka/akka/http/oauth2/client/strategy/AuthorizationCodeStrategy.scala
+++ b/src/main/scala/com/github/dakatsuka/akka/http/oauth2/client/strategy/AuthorizationCodeStrategy.scala
@@ -28,7 +28,7 @@ class AuthorizationCodeStrategy extends Strategy(GrantType.AuthorizationCode) {
       method = config.tokenMethod,
       uri = uri,
       headers = List(
-        RawHeader("Accept", "*/*")
+        RawHeader("Accept", "application/json")
       ),
       FormData(
         params ++ Map(
diff --git a/src/main/scala/com/github/dakatsuka/akka/http/oauth2/client/strategy/ClientCredentialsStrategy.scala b/src/main/scala/com/github/dakatsuka/akka/http/oauth2/client/strategy/ClientCredentialsStrategy.scala
index c805077..7504cf1 100644
--- a/src/main/scala/com/github/dakatsuka/akka/http/oauth2/client/strategy/ClientCredentialsStrategy.scala
+++ b/src/main/scala/com/github/dakatsuka/akka/http/oauth2/client/strategy/ClientCredentialsStrategy.scala
@@ -18,7 +18,7 @@ class ClientCredentialsStrategy extends Strategy(GrantType.ClientCredentials) {
       method = config.tokenMethod,
       uri = uri,
       headers = List(
-        RawHeader("Accept", "*/*")
+        RawHeader("Accept", "application/json")
       ),
       FormData(
         params ++ Map(
diff --git a/src/main/scala/com/github/dakatsuka/akka/http/oauth2/client/strategy/PasswordCredentialsStrategy.scala b/src/main/scala/com/github/dakatsuka/akka/http/oauth2/client/strategy/PasswordCredentialsStrategy.scala
index ba7797d..29ea079 100644
--- a/src/main/scala/com/github/dakatsuka/akka/http/oauth2/client/strategy/PasswordCredentialsStrategy.scala
+++ b/src/main/scala/com/github/dakatsuka/akka/http/oauth2/client/strategy/PasswordCredentialsStrategy.scala
@@ -21,7 +21,7 @@ class PasswordCredentialsStrategy extends Strategy(GrantType.PasswordCredentials
       method = config.tokenMethod,
       uri = uri,
       headers = List(
-        RawHeader("Accept", "*/*")
+        RawHeader("Accept", "application/json")
       ),
       FormData(
         params ++ Map(
diff --git a/src/main/scala/com/github/dakatsuka/akka/http/oauth2/client/strategy/RefreshTokenStrategy.scala b/src/main/scala/com/github/dakatsuka/akka/http/oauth2/client/strategy/RefreshTokenStrategy.scala
index 67e6d55..ed7ec4b 100644
--- a/src/main/scala/com/github/dakatsuka/akka/http/oauth2/client/strategy/RefreshTokenStrategy.scala
+++ b/src/main/scala/com/github/dakatsuka/akka/http/oauth2/client/strategy/RefreshTokenStrategy.scala
@@ -20,7 +20,7 @@ class RefreshTokenStrategy extends Strategy(GrantType.RefreshToken) {
       method = config.tokenMethod,
       uri = uri,
       headers = List(
-        RawHeader("Accept", "*/*")
+        RawHeader("Accept", "application/json")
       ),
       FormData(
         params ++ Map(