diff --git a/dbus-java-core/src/main/java/org/freedesktop/dbus/connections/SASL.java b/dbus-java-core/src/main/java/org/freedesktop/dbus/connections/SASL.java
index 1e9c9e571..60939cba5 100644
--- a/dbus-java-core/src/main/java/org/freedesktop/dbus/connections/SASL.java
+++ b/dbus-java-core/src/main/java/org/freedesktop/dbus/connections/SASL.java
@@ -366,7 +366,8 @@ SaslResult doResponse(int _auth, String _uid, String _kernelUid, SASL.Command _c
                 case AUTH_ANON:
                     return SaslResult.OK;
                 case AUTH_EXTERNAL:
-                    if (0 == COL.compare(_uid, _c.getData()) && (null == _kernelUid || 0 == COL.compare(_uid, _kernelUid))) {
+                    if ((_c.getData() != null && COL.compare(_uid, _c.getData()) == 0)
+                        && (_kernelUid == null || COL.compare(_uid, _kernelUid) == 0)) {
                         return SaslResult.OK;
                     } else {
                         return SaslResult.REJECT;