diff --git a/demboyz/io/conlogwriter.cpp b/demboyz/io/conlogwriter.cpp
index fc0d831..36677ae 100644
--- a/demboyz/io/conlogwriter.cpp
+++ b/demboyz/io/conlogwriter.cpp
@@ -12,7 +12,7 @@ public:
     virtual void StartWriting(demoheader_t& header) override final;
     virtual void EndWriting() override final;
 
-    virtual void StartCommandPacket(CommandPacket& packet) override final;
+    virtual void StartCommandPacket(const CommandPacket& packet) override final;
     virtual void EndCommandPacket(const PacketTrailingBits& trailingBits) override final;
 
     virtual void WriteNetPacket(NetPacket& packet, SourceGameContext& context) override final;
@@ -47,7 +47,7 @@ void ConLogWriter::EndWriting()
     fflush(stdout);
 }
 
-void ConLogWriter::StartCommandPacket(CommandPacket& packet)
+void ConLogWriter::StartCommandPacket(const CommandPacket& packet)
 {
 }
 
diff --git a/demboyz/io/demowriter.cpp b/demboyz/io/demowriter.cpp
index 9c8af33..2dcb060 100644
--- a/demboyz/io/demowriter.cpp
+++ b/demboyz/io/demowriter.cpp
@@ -17,7 +17,7 @@ public:
     virtual void StartWriting(demoheader_t& header) override final;
     virtual void EndWriting() override final;
 
-    virtual void StartCommandPacket(CommandPacket& packet) override final;
+    virtual void StartCommandPacket(const CommandPacket& packet) override final;
     virtual void EndCommandPacket(const PacketTrailingBits& trailingBits) override final;
 
     virtual void WriteNetPacket(NetPacket& packet, SourceGameContext& context) override final;
@@ -49,7 +49,7 @@ void DemoWriter::EndWriting()
 {
 }
 
-void DemoWriter::StartCommandPacket(CommandPacket& packet)
+void DemoWriter::StartCommandPacket(const CommandPacket& packet)
 {
     m_writer.WriteCmdHeader(packet.cmd, packet.tick);
     DemHandlers::DemMsg_FileWrite(packet.cmd, m_writer, packet.data);
diff --git a/demboyz/io/idemowriter.h b/demboyz/io/idemowriter.h
index 0b8842d..28a03ff 100644
--- a/demboyz/io/idemowriter.h
+++ b/demboyz/io/idemowriter.h
@@ -37,7 +37,7 @@ public:
     virtual void StartWriting(demoheader_t& header) = 0;
     virtual void EndWriting() = 0;
 
-    virtual void StartCommandPacket(CommandPacket& packet) = 0;
+    virtual void StartCommandPacket(const CommandPacket& packet) = 0;
     virtual void EndCommandPacket(const PacketTrailingBits& trailingBits) = 0;
 
     virtual void WriteNetPacket(NetPacket& packet, SourceGameContext& context) = 0;
diff --git a/demboyz/io/jsonwriter.cpp b/demboyz/io/jsonwriter.cpp
index bb680e1..4ddf4ba 100644
--- a/demboyz/io/jsonwriter.cpp
+++ b/demboyz/io/jsonwriter.cpp
@@ -10,7 +10,7 @@ public:
     virtual void StartWriting(demoheader_t& header) override final;
     virtual void EndWriting() override final;
 
-    virtual void StartCommandPacket(CommandPacket& packet) override final;
+    virtual void StartCommandPacket(const CommandPacket& packet) override final;
     virtual void EndCommandPacket(const PacketTrailingBits& trailingBits) override final;
 
     virtual void WriteNetPacket(NetPacket& packet, SourceGameContext& context) override final;
@@ -33,7 +33,7 @@ void JsonWriter::EndWriting()
 {
 }
 
-void JsonWriter::StartCommandPacket(CommandPacket& packet)
+void JsonWriter::StartCommandPacket(const CommandPacket& packet)
 {
 }