diff --git a/DataFormats/Headers/include/Headers/DataHeader.h b/DataFormats/Headers/include/Headers/DataHeader.h
index 23a5b8d42d583..a1ea242001f6e 100644
--- a/DataFormats/Headers/include/Headers/DataHeader.h
+++ b/DataFormats/Headers/include/Headers/DataHeader.h
@@ -242,9 +242,9 @@ struct BaseHeader
   /// @brief access header in buffer
   ///
   /// this is to guess if the buffer starting at b looks like a header
-  inline static const BaseHeader* get(byte* b, size_t /*len*/=0) {
-    return (*(reinterpret_cast<uint32_t*>(b))==sMagicString) ?
-      reinterpret_cast<BaseHeader*>(b) :
+  inline static const BaseHeader* get(const byte* b, size_t /*len*/=0) {
+    return (*(reinterpret_cast<const uint32_t*>(b))==sMagicString) ?
+      reinterpret_cast<const BaseHeader*>(b) :
       nullptr;
   }
 
@@ -264,7 +264,7 @@ struct BaseHeader
 /// use like this:
 /// HeaderType* h = get<HeaderType>(buffer)
 template<typename HeaderType>
-const HeaderType* get(byte* buffer, size_t /*len*/=0) {
+const HeaderType* get(const byte* buffer, size_t /*len*/=0) {
   const BaseHeader* current = BaseHeader::get(buffer);
   if (!current) return nullptr;
   if (current->description==HeaderType::sHeaderType)
@@ -304,8 +304,8 @@ struct Block {
   size_t bufferSize;
   Buffer buffer;
 
-  byte* data() {return buffer.get();}
-  size_t size() {return bufferSize;}
+  byte* data() const {return buffer.get();}
+  size_t size() const {return bufferSize;}
 
   ///The magic constructor: takes arbitrary number of arguments and serialized them
   /// into the buffer.
diff --git a/Utilities/O2device/include/O2device/O2device.h b/Utilities/O2device/include/O2device/O2device.h
index 0bd5f5a5617dd..d50a1701038f9 100644
--- a/Utilities/O2device/include/O2device/O2device.h
+++ b/Utilities/O2device/include/O2device/O2device.h
@@ -62,12 +62,11 @@ class O2device : public FairMQDevice
   /// currently this is old school: buf,len pairs;
   /// In the end I'd like to move to array_view
   /// when this becomes available (either with C++17 or via GSL)
-  template<typename T>
-  bool ForEach(O2message& parts,
-               bool (T::* memberFunction)(byte* headerBuffer, size_t headerBufferSize,
-                                          byte* dataBuffer,   size_t dataBufferSize)) {
-
-    if ((parts.Size()%2) != 0)
+  template <typename T>
+  bool ForEach(O2message& parts, bool (T::*memberFunction)(const byte* headerBuffer, size_t headerBufferSize,
+                                                           const byte* dataBuffer, size_t dataBufferSize))
+  {
+    if ((parts.Size() % 2) != 0)
       throw std::invalid_argument("number of parts in message not even (n%2 != 0)");
 
     for (auto it = parts.fParts.begin(); it != parts.fParts.end(); ++it) {
diff --git a/Utilities/fairMQmonitor/include/fairMQmonitor/FairMQmonitor.h b/Utilities/fairMQmonitor/include/fairMQmonitor/FairMQmonitor.h
index bc810c7a6ec67..3f2f859207878 100644
--- a/Utilities/fairMQmonitor/include/fairMQmonitor/FairMQmonitor.h
+++ b/Utilities/fairMQmonitor/include/fairMQmonitor/FairMQmonitor.h
@@ -38,8 +38,8 @@ class FairMQmonitor : public AliceO2::Base::O2device
   virtual void Run();
   void InitTask();
   bool HandleData(AliceO2::Base::O2message& parts, int index);
-  bool HandleO2frame(byte* headerBuffer, size_t headerBufferSize,
-      byte* dataBuffer,   size_t dataBufferSize);
+  bool HandleO2frame(const byte* headerBuffer, size_t headerBufferSize,
+      const byte* dataBuffer,   size_t dataBufferSize);
 
 private:
   AliceO2::Header::DataHeader mDataHeader;
diff --git a/Utilities/fairMQmonitor/src/FairMQmonitor.cxx b/Utilities/fairMQmonitor/src/FairMQmonitor.cxx
index 148ab77e6d85f..612b77af59c13 100644
--- a/Utilities/fairMQmonitor/src/FairMQmonitor.cxx
+++ b/Utilities/fairMQmonitor/src/FairMQmonitor.cxx
@@ -92,8 +92,8 @@ void FairMQmonitor::Run()
 }
 
 //__________________________________________________________________________________________________
-bool FairMQmonitor::HandleO2frame(byte* headerBuffer, size_t headerBufferSize,
-    byte* dataBuffer,   size_t dataBufferSize)
+bool FairMQmonitor::HandleO2frame(const byte* headerBuffer, size_t headerBufferSize,
+    const byte* dataBuffer,   size_t dataBufferSize)
 {
 
   hexDump("headerBuffer", headerBuffer, headerBufferSize);