diff --git a/src/test/avalanche_tests.cpp b/src/test/avalanche_tests.cpp
--- a/src/test/avalanche_tests.cpp
+++ b/src/test/avalanche_tests.cpp
@@ -221,7 +221,11 @@
 
     CBlock block = CreateAndProcessBlock({}, CScript());
     const BlockHash blockHash = block.GetHash();
-    const CBlockIndex *pindex = mapBlockIndex[blockHash];
+    const CBlockIndex *pindex;
+    {
+        LOCK(cs_main);
+        pindex = LookupBlockIndex(blockHash);
+    }
 
     // Create nodes that supports avalanche.
     auto avanodes =
@@ -392,11 +396,16 @@
     // Make sure the block has a hash.
     CBlock blockA = CreateAndProcessBlock({}, CScript());
     const BlockHash blockHashA = blockA.GetHash();
-    const CBlockIndex *pindexA = mapBlockIndex[blockHashA];
 
     CBlock blockB = CreateAndProcessBlock({}, CScript());
     const BlockHash blockHashB = blockB.GetHash();
-    const CBlockIndex *pindexB = mapBlockIndex[blockHashB];
+    const CBlockIndex *pindexA;
+    const CBlockIndex *pindexB;
+    {
+        LOCK(cs_main);
+        pindexA = LookupBlockIndex(blockHashA);
+        pindexB = LookupBlockIndex(blockHashB);
+    }
 
     // Querying for random block returns false.
     BOOST_CHECK(!p.isAccepted(pindexA));
@@ -498,7 +507,11 @@
 
     CBlock block = CreateAndProcessBlock({}, CScript());
     const BlockHash blockHash = block.GetHash();
-    const CBlockIndex *pindex = mapBlockIndex[blockHash];
+    const CBlockIndex *pindex;
+    {
+        LOCK(cs_main);
+        pindex = LookupBlockIndex(blockHash);
+    }
 
     // There is no node to query.
     BOOST_CHECK_EQUAL(AvalancheTest::getSuitableNodeToQuery(p), NO_NODE);
@@ -595,7 +608,11 @@
     // Out of order response are rejected.
     CBlock block2 = CreateAndProcessBlock({}, CScript());
     const BlockHash blockHash2 = block2.GetHash();
-    CBlockIndex *pindex2 = mapBlockIndex[blockHash2];
+    CBlockIndex *pindex2;
+    {
+        LOCK(cs_main);
+        pindex2 = LookupBlockIndex(blockHash2);
+    }
     BOOST_CHECK(p.addBlockToReconcile(pindex2));
 
     resp = {AvalancheTest::getRound(p),
@@ -645,7 +662,11 @@
 
     CBlock block = CreateAndProcessBlock({}, CScript());
     const BlockHash blockHash = block.GetHash();
-    const CBlockIndex *pindex = mapBlockIndex[blockHash];
+    const CBlockIndex *pindex;
+    {
+        LOCK(cs_main);
+        pindex = LookupBlockIndex(blockHash);
+    }
 
     // Add the block
     BOOST_CHECK(p.addBlockToReconcile(pindex));
@@ -715,7 +736,11 @@
     // Add a block to poll
     CBlock block = CreateAndProcessBlock({}, CScript());
     const BlockHash blockHash = block.GetHash();
-    const CBlockIndex *pindex = mapBlockIndex[blockHash];
+    const CBlockIndex *pindex;
+    {
+        LOCK(cs_main);
+        pindex = LookupBlockIndex(blockHash);
+    }
     BOOST_CHECK(p.addBlockToReconcile(pindex));
 
     // Ensure there are enough requests in flight.
@@ -767,7 +792,11 @@
 
     CBlock block = CreateAndProcessBlock({}, CScript());
     const BlockHash blockHash = block.GetHash();
-    const CBlockIndex *pindex = mapBlockIndex[blockHash];
+    const CBlockIndex *pindex;
+    {
+        LOCK(cs_main);
+        pindex = LookupBlockIndex(blockHash);
+    }
 
     // Create nodes that supports avalanche.
     auto avanodes =
@@ -839,7 +868,11 @@
 
     CBlock block = CreateAndProcessBlock({}, CScript());
     const BlockHash blockHash = block.GetHash();
-    const CBlockIndex *pindex = mapBlockIndex[blockHash];
+    const CBlockIndex *pindex;
+    {
+        LOCK(cs_main);
+        pindex = LookupBlockIndex(blockHash);
+    }
 
     // Starting the event loop.
     BOOST_CHECK(p.startEventLoop(s));