diff --git a/src/crypto/groestl.c b/src/crypto/groestl.c
index e1c89cc3b..c8258add3 100644
--- a/src/crypto/groestl.c
+++ b/src/crypto/groestl.c
@@ -8,6 +8,7 @@
  *
  */
 
+#include <stddef.h>
 #include "groestl.h"
 #include "groestl_tables.h"
 
@@ -204,10 +205,9 @@ static void OutputTransformation(hashState *ctx) {
 
 /* initialise context */
 static void Init(hashState* ctx) {
-  int i = 0;
   /* allocate memory for state and data buffer */
 
-  for(;i<(SIZE512/sizeof(uint32_t));i++)
+  for(size_t i = 0; i < (SIZE512/sizeof(uint32_t)); i++)
   {
 	ctx->chaining[i] = 0;
   }
diff --git a/src/crypto/slow-hash.c b/src/crypto/slow-hash.c
index 60699d4e6..679edf7f9 100644
--- a/src/crypto/slow-hash.c
+++ b/src/crypto/slow-hash.c
@@ -413,7 +413,6 @@ BOOL SetLockPagesPrivilege(HANDLE hProcess, BOOL bEnable)
 
 void slow_hash_allocate_state(void)
 {
-    int state = 0;
     if(hp_state != NULL)
         return;
 
diff --git a/src/cryptonote_core/blockchain.cpp b/src/cryptonote_core/blockchain.cpp
index be0a4a6d7..24b82c520 100644
--- a/src/cryptonote_core/blockchain.cpp
+++ b/src/cryptonote_core/blockchain.cpp
@@ -2028,7 +2028,6 @@ bool Blockchain::check_tx_inputs(const transaction& tx, uint64_t* pmax_used_bloc
             return false;
         }
 
-        bool result;
         if (threads > 1)
         {
             // ND: Speedup
@@ -2364,7 +2363,6 @@ bool Blockchain::handle_block_to_main_chain(const block& bl, const crypto::hash&
     uint64_t t_exists = 0;
     uint64_t t_pool = 0;
     uint64_t t_dblspnd = 0;
-    uint64_t t_cc;
     bool add_tx_to_pool = false;
     TIME_MEASURE_FINISH(t3);
 
@@ -2679,7 +2677,6 @@ bool Blockchain::cleanup_handle_incoming_blocks(bool force_sync)
     LOG_PRINT_YELLOW("Blockchain::" << __func__, LOG_LEVEL_3);
     CRITICAL_REGION_LOCAL(m_blockchain_lock);
     TIME_MEASURE_START(t1);
-    auto height = m_db->height();
 
     if (m_sync_counter > 0)
     {
diff --git a/src/cryptonote_core/cryptonote_format_utils.cpp b/src/cryptonote_core/cryptonote_format_utils.cpp
index cac51c042..b679eca50 100644
--- a/src/cryptonote_core/cryptonote_format_utils.cpp
+++ b/src/cryptonote_core/cryptonote_format_utils.cpp
@@ -433,7 +433,6 @@ namespace cryptonote
         if (get_encrypted_payment_id_from_tx_extra_nonce(extra_nonce.nonce, payment_id))
         {
           LOG_PRINT_L2("Encrypting payment id " << payment_id);
-          crypto::key_derivation derivation;
           crypto::public_key view_key_pub = get_destination_view_key_pub(destinations, sender_account_keys);
           if (view_key_pub == null_pkey)
           {