diff --git a/src/disk.ino b/src/disk.ino
index a2c213f..d23f0e2 100755
--- a/src/disk.ino
+++ b/src/disk.ino
@@ -184,6 +184,9 @@ void ConfigureDiskHandlers(VirtualDevice_t *vdev) {
   vdev->m_handler[CMD_MODE_SENSE10]    = &ModeSenseCommandHandler;
   vdev->m_handler[CMD_SEARCH_DATA_EQUAL] = &SearchDataEqualCommandHandler;
   vdev->m_handler[CMD_READ_DEFECT_DATA] = &ReadDefectCommandHandler;
+  vdev->m_handler[CMD_SEND_DIAGNOSTIC] = &SendDiagnosticCommandHandler;
+  vdev->m_handler[CMD_PREFETCH_CACHE10] = &PrefetchCommandHandler;
+  vdev->m_handler[CMD_SYNCHRONIZE_CACHE10] = &SyncCacheCommandHandler;
 #if SUPPORT_SASI
   if(vdev->m_quirks & QUIRKS_SASI)
     vdev->m_handler[CMD_SET_DRIVE_PARAMETER] = &DTCsetDriveParameterCommandHandler;
diff --git a/src/general.ino b/src/general.ino
index 2fdabb4..f62f5df 100755
--- a/src/general.ino
+++ b/src/general.ino
@@ -530,6 +530,24 @@ void SearchDataEqualCommandHandler() {
   m_phase = PHASE_STATUSIN;
 }
 
+void SendDiagnosticCommandHandler() {
+  LOGN("[SendDiagnostic]");
+  if(!m_sel) {
+    m_sts |= STATUS_CHECK; // Image file absent
+    m_phase = PHASE_STATUSIN;
+    return;
+  }
+  if(m_cmd[1] & 0x04) {
+  } else {
+      m_sel->m_sense.m_code = INVALID_FIELD_IN_CDB;    /* "Invalid field in CDB" */
+      m_sel->m_sense.m_key_specific[0] = ERROR_IN_OPCODE;  /* "Error in Byte 1" */
+      m_sel->m_sense.m_key_specific[1] = 0x00;
+      m_sel->m_sense.m_key_specific[2] = 0x01;
+      m_sts |= STATUS_CHECK;
+  }
+  m_phase = PHASE_STATUSIN;
+}
+
 void ReadDefectCommandHandler() {
   LOGN("[ReadDefect]");
   m_responsebuffer[0] = 0x00;
@@ -551,6 +569,16 @@ void PreAllowMediumRemovalCommandHandler() {
   m_phase = PHASE_STATUSIN;
 }
 
+void PrefetchCommandHandler() {
+  LOGN("[Prefetch]");
+  m_phase = PHASE_STATUSIN;
+}
+
+void SyncCacheCommandHandler() {
+  LOGN("[SyncCache]");
+  m_phase = PHASE_STATUSIN;
+}
+
 void UnknownCommandHandler() {
   LOGN("[*Unknown]");
   m_sts |= STATUS_CHECK;
diff --git a/src/optical.ino b/src/optical.ino
index 94703ad..97c470e 100755
--- a/src/optical.ino
+++ b/src/optical.ino
@@ -531,6 +531,7 @@ void ConfigureOpticalHandlers(VirtualDevice_t *vdev) {
   vdev->m_handler[CMD_READ_TOC]                      = &OpticalReadTOCCommandHandler;
   vdev->m_handler[CMD_READ_HEADER]                   = &OpticalHeaderCommandHandler;
   //vdev->m_handler[CMD_GET_CONFIGURATION]             = &OpticalGetConfigurationCommandHandler;
+  vdev->m_handler[CMD_SEND_DIAGNOSTIC] = &SendDiagnosticCommandHandler;
   vdev->m_handler[CMD_GET_EVENT_STATUS_NOTIFICATION] = &OpticalEventStatusCommandHandler;
   vdev->m_handler[CMD_READ_DISC_INFORMATION]         = &OpticalReadDiscInfoCommandHandler;
   vdev->m_handler[CMD_MODE_SELECT10]                 = &ModeSelect10CommandHandler;