diff --git a/rabbit.cpp b/rabbit.cpp
index 7e29526c..2c32f4f0 100644
--- a/rabbit.cpp
+++ b/rabbit.cpp
@@ -195,6 +195,7 @@ void RabbitWithIVPolicy::CipherSetKey(const NameValuePairs &params, const byte *
 void RabbitWithIVPolicy::CipherResynchronize(byte *keystreamBuffer, const byte *iv, size_t length)
 {
 	CRYPTOPP_UNUSED(keystreamBuffer);
+	CRYPTOPP_UNUSED(length);
 	CRYPTOPP_ASSERT(length == 8);
 
 	/* Generate four subvectors */