diff --git a/Marlin/src/gcode/queue.cpp b/Marlin/src/gcode/queue.cpp
index d697baae05f..4e9a47eafee 100644
--- a/Marlin/src/gcode/queue.cpp
+++ b/Marlin/src/gcode/queue.cpp
@@ -367,8 +367,8 @@ void gcode_line_error(PGM_P const err, const int8_t port) {
         stream_state = StreamState::PACKET_TIMEOUT;
         return false;
       }
-      if (!serial_data_available(card.transfer_port)) return false;
-      data = read_serial(card.transfer_port);
+      if (!serial_data_available(card.transfer_port_index)) return false;
+      data = read_serial(card.transfer_port_index);
       packet.timeout = millis() + STREAM_MAX_WAIT;
       return true;
     }
@@ -379,7 +379,7 @@ void gcode_line_error(PGM_P const err, const int8_t port) {
       millis_t transfer_timeout = millis() + RX_TIMESLICE;
 
       #if ENABLED(SDSUPPORT)
-        PORT_REDIRECT(card.transfer_port);
+        PORT_REDIRECT(card.transfer_port_index);
       #endif
 
       while (PENDING(millis(), transfer_timeout)) {
@@ -491,8 +491,8 @@ void gcode_line_error(PGM_P const err, const int8_t port) {
               stream_state = StreamState::PACKET_RESEND;
               break;
             }
-            if (!serial_data_available(card.transfer_port)) break;
-            read_serial(card.transfer_port); // throw away data
+            if (!serial_data_available(card.transfer_port_index)) break;
+            read_serial(card.transfer_port_index); // throw away data
             packet.timeout = millis() + STREAM_MAX_WAIT;
             break;
           case StreamState::PACKET_TIMEOUT:
@@ -558,7 +558,7 @@ inline void get_serial_commands() {
        * receive buffer (which limits the packet size to MAX_CMD_SIZE).
        * The receive buffer also limits the packet size for reliable transmission.
        */
-      binaryStream.receive(serial_line_buffer[card.transfer_port]);
+      binaryStream.receive(serial_line_buffer[card.transfer_port_index]);
       return;
     }
   #endif
diff --git a/Marlin/src/gcode/sdcard/M20-M30_M32-M34_M524_M928.cpp b/Marlin/src/gcode/sdcard/M20-M30_M32-M34_M524_M928.cpp
index f6725358c4d..af8b72ae2e8 100644
--- a/Marlin/src/gcode/sdcard/M20-M30_M32-M34_M524_M928.cpp
+++ b/Marlin/src/gcode/sdcard/M20-M30_M32-M34_M524_M928.cpp
@@ -192,7 +192,7 @@ void GcodeSuite::M28() {
       SERIAL_ECHOLN(p);
       card.openFile(p, false);
       #if NUM_SERIAL > 1
-        card.transfer_port = command_queue_port[cmd_queue_index_r];
+        card.transfer_port_index = command_queue_port[cmd_queue_index_r];
       #endif
     }
     else
diff --git a/Marlin/src/sd/cardreader.cpp b/Marlin/src/sd/cardreader.cpp
index 971f8955708..d76bbe8c970 100644
--- a/Marlin/src/sd/cardreader.cpp
+++ b/Marlin/src/sd/cardreader.cpp
@@ -52,7 +52,7 @@ char CardReader::filename[FILENAME_LENGTH], CardReader::longFilename[LONG_FILENA
 int8_t CardReader::autostart_index;
 
 #if ENABLED(BINARY_FILE_TRANSFER) && NUM_SERIAL > 1
-  int8_t CardReader::transfer_port;
+  int8_t CardReader::transfer_port_index;
 #endif
 
 // private:
diff --git a/Marlin/src/sd/cardreader.h b/Marlin/src/sd/cardreader.h
index 4e86be70f1d..a13633eafe0 100644
--- a/Marlin/src/sd/cardreader.h
+++ b/Marlin/src/sd/cardreader.h
@@ -147,9 +147,9 @@ public:
 
   #if ENABLED(BINARY_FILE_TRANSFER)
     #if NUM_SERIAL > 1
-      static int8_t transfer_port;
+      static int8_t transfer_port_index;
     #else
-      static constexpr int8_t transfer_port = 0;
+      static constexpr int8_t transfer_port_index = 0;
     #endif
   #endif