diff --git a/src/BlueSCSI.cpp b/src/BlueSCSI.cpp
index 6aff9c3..4478f79 100644
--- a/src/BlueSCSI.cpp
+++ b/src/BlueSCSI.cpp
@@ -1597,7 +1597,7 @@ void loop()
   // proper full size SCSI command byte to follow
   // so just read it and re-read it again to get the
   // real command byte
-  if(cmd[0] == 0x1F) { cmd[0] = readHandshake(); }
+  if(cmd[0] == SCSI_ICD_EXTENDED_CMD) { cmd[0] = readHandshake(); }
 
   LOGHEX(cmd[0]);
   // Command length selection, reception
diff --git a/src/scsi_cmds.h b/src/scsi_cmds.h
index f8f20f2..28b07c7 100644
--- a/src/scsi_cmds.h
+++ b/src/scsi_cmds.h
@@ -21,6 +21,7 @@
 #define SCSI_RECV_DIAG_RESULTS      0x1C
 #define SCSI_SEND_DIAG              0x1D
 #define SCSI_PREVENT_ALLOW_REMOVAL  0x1E
+#define SCSI_ICD_EXTENDED_CMD       0x1F
 #define SCSI_READ_CAPACITY          0x25
 #define SCSI_READ10                 0x28
 #define SCSI_WRITE10                0x2A