diff --git a/Firmware/fibre/cpp/include/fibre/protocol.hpp b/Firmware/fibre/cpp/include/fibre/protocol.hpp
index 016d7064..bfe774db 100644
--- a/Firmware/fibre/cpp/include/fibre/protocol.hpp
+++ b/Firmware/fibre/cpp/include/fibre/protocol.hpp
@@ -1,3 +1,5 @@
+#pragma GCC optimize ("O3")
+
 /*
 see protocol.md for the protocol specification
 */
@@ -1098,6 +1100,7 @@ public:
 extern Endpoint** endpoint_list_;
 extern size_t n_endpoints_;
 extern uint16_t json_crc_;
+extern uint32_t json_fibre_cache_entropy_;
 extern JSONDescriptorEndpoint json_file_endpoint_;
 extern EndpointProvider* application_endpoints_;
 
@@ -1124,12 +1127,16 @@ int fibre_publish(T& application_objects) {
     // Calculate the CRC16 of the JSON file.
     // The init value is the protocol version.
     CRC16Calculator crc16_calculator(PROTOCOL_VERSION);
+
     uint8_t offset[4] = { 0 };
     json_file_endpoint_.handle(offset, sizeof(offset), &crc16_calculator);
     json_crc_ = crc16_calculator.get_crc16();
 
+    // Add entropy for fibre cache
+    json_file_endpoint_.handle(offset, sizeof(offset), &crc16_calculator);
+    json_fibre_cache_entropy_ = (uint32_t) crc16_calculator.get_crc16();
+    json_fibre_cache_entropy_ += json_crc_ << 16;
+
     return 0;
 }
-
-
 #endif