diff --git a/src/cc/eval.cpp b/src/cc/eval.cpp
index b8044e0dd..2405c2375 100644
--- a/src/cc/eval.cpp
+++ b/src/cc/eval.cpp
@@ -84,7 +84,7 @@ bool Eval::GetSpendsConfirmed(uint256 hash, std::vector<CTransaction> &spends) c
 }
 
 
-bool Eval::GetTxUnconfirmed(const uint256 &hash, CTransaction &txOut, uint256 &hashBlock) const
+bool Eval::GetTxUnconfirmed(const uint256 &hash, const CTransaction &txOut, uint256 &hashBlock) const
 {
     bool fAllowSlow = false; // Don't allow slow
     return GetTransaction(hash, txOut, hashBlock, fAllowSlow);
diff --git a/src/cc/eval.h b/src/cc/eval.h
index 96af359f1..edff3d96b 100644
--- a/src/cc/eval.h
+++ b/src/cc/eval.h
@@ -81,7 +81,7 @@ public:
     /*
      * IO functions
      */
-    virtual bool GetTxUnconfirmed(const uint256 &hash, CTransaction &txOut, uint256 &hashBlock) const;
+    virtual bool GetTxUnconfirmed(const uint256 &hash, const CTransaction &txOut, uint256 &hashBlock) const;
     virtual bool GetTxConfirmed(const uint256 &hash, CTransaction &txOut, CBlockIndex &block) const;
     virtual unsigned int GetCurrentHeight() const;
     virtual bool GetSpendsConfirmed(uint256 hash, std::vector<CTransaction> &spends) const;