diff --git a/hw/scsi-bus.c b/hw/scsi-bus.c
index 6f0d039..d6fd19a 100644
--- a/hw/scsi-bus.c
+++ b/hw/scsi-bus.c
@@ -977,7 +977,7 @@
         [ LOCATE_16                ] = "LOCATE_16",
         [ WRITE_SAME_16            ] = "WRITE_SAME_16",
         [ ERASE_16                 ] = "ERASE_16",
-        [ SERVICE_ACTION_IN        ] = "SERVICE_ACTION_IN",
+        [ SERVICE_ACTION_IN_16     ] = "SERVICE_ACTION_IN_16",
         [ WRITE_LONG_16            ] = "WRITE_LONG_16",
         [ REPORT_LUNS              ] = "REPORT_LUNS",
         [ BLANK                    ] = "BLANK",
@@ -987,6 +987,7 @@
         [ LOAD_UNLOAD              ] = "LOAD_UNLOAD",
         [ READ_12                  ] = "READ_12",
         [ WRITE_12                 ] = "WRITE_12",
+        [ SERVICE_ACTION_IN_12     ] = "SERVICE_ACTION_IN_12",
         [ WRITE_VERIFY_12          ] = "WRITE_VERIFY_12",
         [ VERIFY_12                ] = "VERIFY_12",
         [ SEARCH_HIGH_12           ] = "SEARCH_HIGH_12",
diff --git a/hw/scsi-defs.h b/hw/scsi-defs.h
index ea288fa..bfe9392 100644
--- a/hw/scsi-defs.h
+++ b/hw/scsi-defs.h
@@ -102,7 +102,7 @@
 #define LOCATE_16             0x92
 #define WRITE_SAME_16         0x93
 #define ERASE_16              0x93
-#define SERVICE_ACTION_IN     0x9e
+#define SERVICE_ACTION_IN_16  0x9e
 #define WRITE_LONG_16         0x9f
 #define REPORT_LUNS           0xa0
 #define BLANK                 0xa1
@@ -112,6 +112,7 @@
 #define LOAD_UNLOAD           0xa6
 #define READ_12               0xa8
 #define WRITE_12              0xaa
+#define SERVICE_ACTION_IN_12  0xab
 #define WRITE_VERIFY_12       0xae
 #define VERIFY_12             0xaf
 #define SEARCH_HIGH_12        0xb0
@@ -123,6 +124,11 @@
 #define SET_CD_SPEED          0xbb
 
 /*
+ * SERVICE ACTION IN subcodes
+ */
+#define SAI_READ_CAPACITY_16  0x10
+
+/*
  *  SAM Status codes
  */
 
diff --git a/hw/scsi-disk.c b/hw/scsi-disk.c
index c23c2b8..ead4163 100644
--- a/hw/scsi-disk.c
+++ b/hw/scsi-disk.c
@@ -890,9 +890,9 @@
         outbuf[7] = 8; // CD-ROM
         buflen = 8;
         break;
-    case SERVICE_ACTION_IN:
+    case SERVICE_ACTION_IN_16:
         /* Service Action In subcommands. */
-        if ((req->cmd.buf[1] & 31) == 0x10) {
+        if ((req->cmd.buf[1] & 31) == SAI_READ_CAPACITY_16) {
             DPRINTF("SAI READ CAPACITY(16)\n");
             memset(outbuf, 0, req->cmd.xfer);
             bdrv_get_geometry(s->bs, &nb_sectors);
@@ -992,7 +992,7 @@
     case READ_CAPACITY_10:
     case READ_TOC:
     case GET_CONFIGURATION:
-    case SERVICE_ACTION_IN:
+    case SERVICE_ACTION_IN_16:
     case VERIFY_10:
         rc = scsi_disk_emulate_command(r, outbuf);
         if (rc < 0) {