diff --git a/hw/scsi/esp.c b/hw/scsi/esp.c
index 64680b3809..baa0a2cfdf 100644
--- a/hw/scsi/esp.c
+++ b/hw/scsi/esp.c
@@ -248,6 +248,8 @@ static void esp_do_dma(ESPState *s)
     len = s->dma_left;
     if (s->do_cmd) {
         trace_esp_do_dma(s->cmdlen, len);
+        assert (s->cmdlen <= sizeof(s->cmdbuf) &&
+                len <= sizeof(s->cmdbuf) - s->cmdlen);
         s->dma_memory_read(s->dma_opaque, &s->cmdbuf[s->cmdlen], len);
         return;
     }
@@ -345,7 +347,7 @@ static void handle_ti(ESPState *s)
     s->dma_counter = dmalen;
 
     if (s->do_cmd)
-        minlen = (dmalen < 32) ? dmalen : 32;
+        minlen = (dmalen < ESP_CMDBUF_SZ) ? dmalen : ESP_CMDBUF_SZ;
     else if (s->ti_size < 0)
         minlen = (dmalen < -s->ti_size) ? dmalen : -s->ti_size;
     else
@@ -449,7 +451,7 @@ void esp_reg_write(ESPState *s, uint32_t saddr, uint64_t val)
         break;
     case ESP_FIFO:
         if (s->do_cmd) {
-            if (s->cmdlen < TI_BUFSZ) {
+            if (s->cmdlen < ESP_CMDBUF_SZ) {
                 s->cmdbuf[s->cmdlen++] = val & 0xff;
             } else {
                 trace_esp_error_fifo_overrun();
diff --git a/include/hw/scsi/esp.h b/include/hw/scsi/esp.h
index 6c795276c9..d2c48869e1 100644
--- a/include/hw/scsi/esp.h
+++ b/include/hw/scsi/esp.h
@@ -14,6 +14,7 @@ void esp_init(hwaddr espaddr, int it_shift,
 
 #define ESP_REGS 16
 #define TI_BUFSZ 16
+#define ESP_CMDBUF_SZ 32
 
 typedef struct ESPState ESPState;
 
@@ -31,7 +32,7 @@ struct ESPState {
     SCSIBus bus;
     SCSIDevice *current_dev;
     SCSIRequest *current_req;
-    uint8_t cmdbuf[TI_BUFSZ];
+    uint8_t cmdbuf[ESP_CMDBUF_SZ];
     uint32_t cmdlen;
     uint32_t do_cmd;