diff --git a/src/net.cpp b/src/net.cpp
index a31b2a5efc..8e596cb6b3 100644
--- a/src/net.cpp
+++ b/src/net.cpp
@@ -932,7 +932,8 @@ CNetMessage V1TransportDeserializer::GetMessage(const std::chrono::microseconds
     return msg;
 }
 
-void V1TransportSerializer::prepareForTransport(CSerializedNetMsg& msg, std::vector<unsigned char>& header) {
+void V1TransportSerializer::prepareForTransport(CSerializedNetMsg& msg, std::vector<unsigned char>& header) const
+{
     // create dbl-sha256 checksum
     uint256 hash = Hash(msg.data);
 
@@ -4126,7 +4127,9 @@ ServiceFlags CConnman::GetLocalServices() const
 unsigned int CConnman::GetReceiveFloodSize() const { return nReceiveFloodSize; }
 
 CNode::CNode(NodeId idIn, ServiceFlags nLocalServicesIn, std::shared_ptr<Sock> sock, const CAddress& addrIn, uint64_t nKeyedNetGroupIn, uint64_t nLocalHostNonceIn, const CAddress& addrBindIn, const std::string& addrNameIn, ConnectionType conn_type_in, bool inbound_onion, std::unique_ptr<i2p::sam::Session>&& i2p_sam_session)
-    : m_sock{sock},
+    : m_deserializer{std::make_unique<V1TransportDeserializer>(V1TransportDeserializer(Params(), idIn, SER_NETWORK, INIT_PROTO_VERSION))},
+      m_serializer{std::make_unique<V1TransportSerializer>(V1TransportSerializer())},
+      m_sock{sock},
       m_connected{GetTime<std::chrono::seconds>()},
       addr{addrIn},
       addrBind{addrBindIn},
@@ -4150,9 +4153,6 @@ CNode::CNode(NodeId idIn, ServiceFlags nLocalServicesIn, std::shared_ptr<Sock> s
     } else {
         LogPrint(BCLog::NET, "Added connection peer=%d\n", id);
     }
-
-    m_deserializer = std::make_unique<V1TransportDeserializer>(V1TransportDeserializer(Params(), id, SER_NETWORK, INIT_PROTO_VERSION));
-    m_serializer = std::make_unique<V1TransportSerializer>(V1TransportSerializer());
 }
 
 bool CConnman::NodeFullyConnected(const CNode* pnode)
diff --git a/src/net.h b/src/net.h
index e2d258e703..def5098b38 100644
--- a/src/net.h
+++ b/src/net.h
@@ -427,13 +427,13 @@ public:
 class TransportSerializer {
 public:
     // prepare message for transport (header construction, error-correction computation, payload encryption, etc.)
-    virtual void prepareForTransport(CSerializedNetMsg& msg, std::vector<unsigned char>& header) = 0;
+    virtual void prepareForTransport(CSerializedNetMsg& msg, std::vector<unsigned char>& header) const = 0;
     virtual ~TransportSerializer() {}
 };
 
-class V1TransportSerializer  : public TransportSerializer {
+class V1TransportSerializer : public TransportSerializer {
 public:
-    void prepareForTransport(CSerializedNetMsg& msg, std::vector<unsigned char>& header) override;
+    void prepareForTransport(CSerializedNetMsg& msg, std::vector<unsigned char>& header) const override;
 };
 
 /** Information about a peer */
@@ -443,10 +443,10 @@ class CNode
     friend struct ConnmanTestMsg;
 
 public:
-    std::unique_ptr<TransportDeserializer> m_deserializer;
-    std::unique_ptr<TransportSerializer> m_serializer;
+    const std::unique_ptr<TransportDeserializer> m_deserializer; // Used only by SocketHandler thread
+    const std::unique_ptr<const TransportSerializer> m_serializer;
 
-    NetPermissionFlags m_permissionFlags{ NetPermissionFlags::None };
+    NetPermissionFlags m_permissionFlags{NetPermissionFlags::None}; // treated as const outside of fuzz tester
     std::atomic<ServiceFlags> nServices{NODE_NONE};
 
     /**
@@ -472,7 +472,7 @@ public:
 
     RecursiveMutex cs_vProcessMsg;
     std::list<CNetMessage> vProcessMsg GUARDED_BY(cs_vProcessMsg);
-    size_t nProcessQueueSize{0};
+    size_t nProcessQueueSize GUARDED_BY(cs_vProcessMsg){0};
 
     RecursiveMutex cs_sendProcessing;
 
@@ -501,7 +501,7 @@ public:
      * from the wire. This cleaned string can safely be logged or displayed.
      */
     std::string cleanSubVer GUARDED_BY(m_subver_mutex){};
-    bool m_prefer_evict{false}; // This peer is preferred for eviction.
+    bool m_prefer_evict{false}; // This peer is preferred for eviction. (treated as const)
     bool HasPermission(NetPermissionFlags permission) const {
         return NetPermissions::HasFlag(m_permissionFlags, permission);
     }
diff --git a/src/net_processing.cpp b/src/net_processing.cpp
index c7cb7cb82a..77ed5bb9b2 100644
--- a/src/net_processing.cpp
+++ b/src/net_processing.cpp
@@ -519,14 +519,14 @@ private:
     std::atomic<int> m_best_height{-1};
 
     /** Next time to check for stale tip */
-    std::chrono::seconds m_stale_tip_check_time{0s};
+    std::chrono::seconds m_stale_tip_check_time GUARDED_BY(cs_main){0s};
 
     /** Whether this node is running in blocks only mode */
     const bool m_ignore_incoming_txs;
 
     /** Whether we've completed initial sync yet, for determining when to turn
       * on extra block-relay-only peers. */
-    bool m_initial_sync_finished{false};
+    bool m_initial_sync_finished GUARDED_BY(cs_main){false};
 
     /** Protects m_peer_map. This mutex must not be locked while holding a lock
      *  on any of the mutexes inside a Peer object. */