diff --git a/openid-connect-client/src/main/java/org/mitre/openid/connect/client/OIDCAuthenticationToken.java b/openid-connect-client/src/main/java/org/mitre/openid/connect/client/OIDCAuthenticationToken.java
index 1395a4b3f..b839cb81a 100644
--- a/openid-connect-client/src/main/java/org/mitre/openid/connect/client/OIDCAuthenticationToken.java
+++ b/openid-connect-client/src/main/java/org/mitre/openid/connect/client/OIDCAuthenticationToken.java
@@ -35,7 +35,7 @@ public class OIDCAuthenticationToken extends AbstractAuthenticationToken {
 
 	private static final long serialVersionUID = 22100073066377804L;
 
-	private final Object principal;
+	private final ImmutableMap<String, String> principal;
 	private final String idTokenValue; // string representation of the id token
 	private final String accessTokenValue; // string representation of the access token
 	private final String refreshTokenValue; // string representation of the refresh token