diff --git a/oauthproxy.go b/oauthproxy.go
index 508084c8..82f265f8 100644
--- a/oauthproxy.go
+++ b/oauthproxy.go
@@ -721,15 +721,17 @@ func (p *OAuthProxy) UserInfo(rw http.ResponseWriter, req *http.Request) {
 	}
 
 	userInfo := struct {
-		User              string   `json:"user"`
-		Email             string   `json:"email"`
-		Groups            []string `json:"groups,omitempty"`
-		PreferredUsername string   `json:"preferredUsername,omitempty"`
+		User              string                 `json:"user"`
+		Email             string                 `json:"email"`
+		Groups            []string               `json:"groups,omitempty"`
+		PreferredUsername string                 `json:"preferredUsername,omitempty"`
+		AdditionalClaims  map[string]interface{} `json:"additionalClaims,omitempty"`
 	}{
 		User:              session.User,
 		Email:             session.Email,
 		Groups:            session.Groups,
 		PreferredUsername: session.PreferredUsername,
+		AdditionalClaims:  session.AdditionalClaims,
 	}
 
 	if err := json.NewEncoder(rw).Encode(userInfo); err != nil {
diff --git a/oauthproxy_test.go b/oauthproxy_test.go
index ccabdbbd..b1411e4c 100644
--- a/oauthproxy_test.go
+++ b/oauthproxy_test.go
@@ -1032,6 +1032,20 @@ func TestUserInfoEndpointAccepted(t *testing.T) {
 			},
 			expectedResponse: "{\"user\":\"john.doe\",\"email\":\"john.doe@example.com\",\"groups\":[\"example\",\"groups\"],\"preferredUsername\":\"john\"}\n",
 		},
+		{
+			name: "With Additional Claim",
+			session: &sessions.SessionState{
+				User:              "john.doe",
+				PreferredUsername: "john",
+				Email:             "john.doe@example.com",
+				Groups:            []string{"example", "groups"},
+				AccessToken:       "my_access_token",
+				AdditionalClaims: map[string]interface{}{
+					"foo": "bar",
+				},
+			},
+			expectedResponse: "{\"user\":\"john.doe\",\"email\":\"john.doe@example.com\",\"groups\":[\"example\",\"groups\"],\"preferredUsername\":\"john\",\"additionalClaims\":{\"foo\":\"bar\"}}\n",
+		},
 	}
 
 	for _, tc := range testCases {