diff --git a/threefish.cpp b/threefish.cpp
index 8ec51762..66bef801 100644
--- a/threefish.cpp
+++ b/threefish.cpp
@@ -272,17 +272,7 @@ void Threefish::Base::UncheckedSetKey(const byte *key, unsigned int keylen, cons
     }
 
     m_tweak.New(3);
-    ConstByteArrayParameter t;
-    if (params.GetValue(Name::Tweak(), t))
-    {
-        CRYPTOPP_ASSERT(t.size() == 16);
-        ::memcpy(m_tweak.begin(), t.begin(), 16);
-        m_tweak[2] = m_tweak[0] + m_tweak[1];
-    }
-    else
-    {
-        ::memset(m_tweak.begin(), 0x00, 24);
-    }
+    ::memset(m_tweak.begin(), 0x00, 24);
 }
 
 void Threefish::Base::ProcessAndXorBlock(const byte *inBlock, const byte *xorBlock, byte *outBlock) const