diff --git a/src/qt/clientmodel.cpp b/src/qt/clientmodel.cpp
--- a/src/qt/clientmodel.cpp
+++ b/src/qt/clientmodel.cpp
@@ -27,8 +27,6 @@
 
 #include <cstdint>
 
-class CBlockIndex;
-
 static int64_t nLastHeaderTipUpdateNotification = 0;
 static int64_t nLastBlockTipUpdateNotification = 0;
 
diff --git a/src/test/miner_tests.cpp b/src/test/miner_tests.cpp
--- a/src/test/miner_tests.cpp
+++ b/src/test/miner_tests.cpp
@@ -263,7 +263,7 @@
                               "de5c384df7ba0b8d578a4c702b6bf11d5f")
                   << OP_CHECKSIG;
     std::unique_ptr<CBlockTemplate> pblocktemplate;
-    CMutableTransaction tx, tx2;
+    CMutableTransaction tx;
     CScript script;
     TestMemPoolEntryHelper entry;
     entry.nFee = 11 * SATOSHI;
diff --git a/src/test/transaction_tests.cpp b/src/test/transaction_tests.cpp
--- a/src/test/transaction_tests.cpp
+++ b/src/test/transaction_tests.cpp
@@ -537,7 +537,6 @@
 
     CTransactionRef output1, output2;
     CMutableTransaction input1, input2;
-    SignatureData sigdata;
 
     // Normal pay-to-compressed-pubkey.
     CreateCreditAndSpend(keystore, scriptPubkey1, output1, input1);
diff --git a/src/txmempool.cpp b/src/txmempool.cpp
--- a/src/txmempool.cpp
+++ b/src/txmempool.cpp
@@ -808,7 +808,6 @@
     while (!waitingOnDependants.empty()) {
         const CTxMemPoolEntry *entry = waitingOnDependants.front();
         waitingOnDependants.pop_front();
-        CValidationState state;
         if (!mempoolDuplicate.HaveInputs(entry->GetTx())) {
             waitingOnDependants.push_back(entry);
             stepsSinceLastRemove++;