diff --git a/src/blockchain_db/berkeleydb/db_bdb.cpp b/src/blockchain_db/berkeleydb/db_bdb.cpp
index 4b254500..221c0cf2 100644
--- a/src/blockchain_db/berkeleydb/db_bdb.cpp
+++ b/src/blockchain_db/berkeleydb/db_bdb.cpp
@@ -502,7 +502,7 @@ void BlockchainBDB::remove_spent_key(const crypto::key_image& k_image)
       throw1(DB_ERROR("Error adding removal of key image to db transaction"));
 }
 
-blobdata BlockchainBDB::output_to_blob(const tx_out& output)
+blobdata BlockchainBDB::output_to_blob(const tx_out& output) const
 {
   LOG_PRINT_L3("BlockchainBDB::" << __func__);
   blobdata b;
diff --git a/src/blockchain_db/berkeleydb/db_bdb.h b/src/blockchain_db/berkeleydb/db_bdb.h
index d4eb5434..83588b03 100644
--- a/src/blockchain_db/berkeleydb/db_bdb.h
+++ b/src/blockchain_db/berkeleydb/db_bdb.h
@@ -232,7 +232,7 @@ private:
    *
    * @return the resultant blob
    */
-  blobdata output_to_blob(const tx_out& output);
+  blobdata output_to_blob(const tx_out& output) const;
 
   /**
    * @brief convert a tx output blob to a tx output
diff --git a/src/blockchain_db/blockchain_db.cpp b/src/blockchain_db/blockchain_db.cpp
index d648be44..bfe93948 100644
--- a/src/blockchain_db/blockchain_db.cpp
+++ b/src/blockchain_db/blockchain_db.cpp
@@ -129,7 +129,7 @@ void BlockchainDB::pop_block(block& blk, std::vector<transaction>& txs)
   }
 }
 
-bool BlockchainDB::is_open()
+bool BlockchainDB::is_open() const
 {
   return m_open;
 }
diff --git a/src/blockchain_db/blockchain_db.h b/src/blockchain_db/blockchain_db.h
index 04d9c538..46c86012 100644
--- a/src/blockchain_db/blockchain_db.h
+++ b/src/blockchain_db/blockchain_db.h
@@ -330,7 +330,7 @@ public:
   virtual void open(const std::string& filename, const int db_flags = 0) = 0;
 
   // returns true of the db is open/ready, else false
-  bool is_open();
+  bool is_open() const;
 
   // close and sync the db
   virtual void close() = 0;
diff --git a/src/blockchain_db/lmdb/db_lmdb.cpp b/src/blockchain_db/lmdb/db_lmdb.cpp
index 7d06ae57..4ea349f7 100644
--- a/src/blockchain_db/lmdb/db_lmdb.cpp
+++ b/src/blockchain_db/lmdb/db_lmdb.cpp
@@ -212,7 +212,7 @@ void mdb_txn_safe::abort()
   }
 }
 
-uint64_t mdb_txn_safe::num_active_tx()
+uint64_t mdb_txn_safe::num_active_tx() const
 {
   return num_active_txns;
 }
@@ -273,7 +273,7 @@ void BlockchainLMDB::do_resize()
   mdb_txn_safe::allow_new_txns();
 }
 
-bool BlockchainLMDB::need_resize()
+bool BlockchainLMDB::need_resize() const
 {
   MDB_envinfo mei;
 
@@ -668,7 +668,7 @@ void BlockchainLMDB::remove_spent_key(const crypto::key_image& k_image)
       throw1(DB_ERROR("Error adding removal of key image to db transaction"));
 }
 
-blobdata BlockchainLMDB::output_to_blob(const tx_out& output)
+blobdata BlockchainLMDB::output_to_blob(const tx_out& output) const
 {
   LOG_PRINT_L3("BlockchainLMDB::" << __func__);
   blobdata b;
diff --git a/src/blockchain_db/lmdb/db_lmdb.h b/src/blockchain_db/lmdb/db_lmdb.h
index ec552a0f..6a264681 100644
--- a/src/blockchain_db/lmdb/db_lmdb.h
+++ b/src/blockchain_db/lmdb/db_lmdb.h
@@ -59,7 +59,7 @@ struct mdb_txn_safe
     return &m_txn;
   }
 
-  uint64_t num_active_tx();
+  uint64_t num_active_tx() const;
 
   static void prevent_new_txns();
   static void wait_no_active_txns();
@@ -201,7 +201,7 @@ public:
 private:
   void do_resize();
 
-  bool need_resize();
+  bool need_resize() const;
 
   virtual void add_block( const block& blk
                 , const size_t& block_size
@@ -236,7 +236,7 @@ private:
    *
    * @return the resultant blob
    */
-  blobdata output_to_blob(const tx_out& output);
+  blobdata output_to_blob(const tx_out& output) const;
 
   /**
    * @brief convert a tx output blob to a tx output