diff --git a/core/src/main/java/org/bitcoinj/core/Message.java b/core/src/main/java/org/bitcoinj/core/Message.java
index 7e156c210a5..9db2d76b4ae 100644
--- a/core/src/main/java/org/bitcoinj/core/Message.java
+++ b/core/src/main/java/org/bitcoinj/core/Message.java
@@ -93,7 +93,7 @@ protected Message(NetworkParameters params, byte[] payload, int offset, int prot
 
         parse();
 
-        if (this.length == UNKNOWN_LENGTH)
+        if (this.length == UNKNOWN_LENGTH && !(this instanceof UnknownMessage))
             checkState(false, "Length field has not been set in constructor for %s after parse.",
                        getClass().getSimpleName());