diff --git a/src/txdb.h b/src/txdb.h
index 68042880a..0b0ac376c 100644
--- a/src/txdb.h
+++ b/src/txdb.h
@@ -97,7 +97,7 @@ public:
     bool ReadLastBlockFile(int &nFile) const;
     bool WriteReindexing(bool fReindex);
     bool ReadReindexing(bool &fReindex) const;
-    bool ReadTxIndex(const uint256 &txid, CDiskTxPos &pos);
+    bool ReadTxIndex(const uint256 &txid, CDiskTxPos &pos) const;
     bool WriteTxIndex(const std::vector<std::pair<uint256, CDiskTxPos> > &list);
     bool ReadSpentIndex(CSpentIndexKey &key, CSpentIndexValue &value) const;
     bool UpdateSpentIndex(const std::vector<std::pair<CSpentIndexKey, CSpentIndexValue> >&vect);