diff --git a/src/emucore/Cart.hxx b/src/emucore/Cart.hxx
index 0a854024a..7acec2d59 100644
--- a/src/emucore/Cart.hxx
+++ b/src/emucore/Cart.hxx
@@ -52,7 +52,7 @@ class Cartridge : public Device
     /**
       Callback type for general cart messages
     */
-    using messageCallback = std::function<void(const string&)>;   
+    using messageCallback = std::function<void(const string&)>;
 
     // Maximum size of a ROM cart that Stella can support
     static constexpr size_t maxSize() { return 512_KB; }
@@ -144,10 +144,10 @@ class Cartridge : public Device
     /**
       Set the callback for displaying messages
     */
-    void setMessageCallback(const messageCallback& callback)
+    void setMessageCallback(messageCallback callback)
     {
-      if(myMsgCallback == nullptr)
-        myMsgCallback = &callback;
+      if(!myMsgCallback)
+        myMsgCallback = callback;
     }
 
   #ifdef DEBUGGER_SUPPORT
@@ -415,7 +415,7 @@ class Cartridge : public Device
     uInt32 myAccessSize;
 
     // Callback to output messages
-    const messageCallback* myMsgCallback{nullptr};
+    messageCallback myMsgCallback{nullptr};
 
   private:
     // The startup bank to use (where to look for the reset vector address)
diff --git a/src/emucore/CartAR.cxx b/src/emucore/CartAR.cxx
index b62fd7daa..d3283610c 100644
--- a/src/emucore/CartAR.cxx
+++ b/src/emucore/CartAR.cxx
@@ -306,7 +306,7 @@ void CartridgeAR::loadIntoRAM(uInt8 load)
       if(checksum(myHeader.data(), 8) != 0x55)
       {
         cerr << "WARNING: The Supercharger header checksum is invalid...\n";
-        (*myMsgCallback)("Supercharger load #" + std::to_string(load) + " done with hearder checksum error");
+        myMsgCallback("Supercharger load #" + std::to_string(load) + " done with hearder checksum error");
         success = false;
       }
 
@@ -322,7 +322,7 @@ void CartridgeAR::loadIntoRAM(uInt8 load)
         if(!invalidPageChecksumSeen && (sum != 0x55))
         {
           cerr << "WARNING: Some Supercharger page checksums are invalid...\n";
-          (*myMsgCallback)("Supercharger load #" + std::to_string(load) + " done with page #"
+          myMsgCallback("Supercharger load #" + std::to_string(load) + " done with page #"
                            + std::to_string(j) + " checksum error");
           invalidPageChecksumSeen = true;
         }
@@ -341,7 +341,7 @@ void CartridgeAR::loadIntoRAM(uInt8 load)
 
       myBankChanged = true;
       if(success)
-        (*myMsgCallback)("Supercharger load #" + std::to_string(load) + " done");
+        myMsgCallback("Supercharger load #" + std::to_string(load) + " done");
       return;
     }
   }