diff --git a/docs/interop/nbd.txt b/docs/interop/nbd.txt
index 6dfec7f476..4511880961 100644
--- a/docs/interop/nbd.txt
+++ b/docs/interop/nbd.txt
@@ -53,4 +53,5 @@ the operation of that feature.
 * 2.12: NBD_CMD_BLOCK_STATUS for "base:allocation"
 * 3.0: NBD_OPT_STARTTLS with TLS Pre-Shared Keys (PSK),
 NBD_CMD_BLOCK_STATUS for "qemu:dirty-bitmap:", NBD_CMD_CACHE
-* 4.2: NBD_FLAG_CAN_MULTI_CONN for sharable read-only exports
+* 4.2: NBD_FLAG_CAN_MULTI_CONN for sharable read-only exports,
+NBD_CMD_FLAG_FAST_ZERO
diff --git a/include/block/nbd.h b/include/block/nbd.h
index 2c87b42dfd..21550747cf 100644
--- a/include/block/nbd.h
+++ b/include/block/nbd.h
@@ -140,6 +140,7 @@ enum {
     NBD_FLAG_CAN_MULTI_CONN_BIT     =  8, /* Multi-client cache consistent */
     NBD_FLAG_SEND_RESIZE_BIT        =  9, /* Send resize */
     NBD_FLAG_SEND_CACHE_BIT         = 10, /* Send CACHE (prefetch) */
+    NBD_FLAG_SEND_FAST_ZERO_BIT     = 11, /* FAST_ZERO flag for WRITE_ZEROES */
 };
 
 #define NBD_FLAG_HAS_FLAGS         (1 << NBD_FLAG_HAS_FLAGS_BIT)
@@ -153,6 +154,7 @@ enum {
 #define NBD_FLAG_CAN_MULTI_CONN    (1 << NBD_FLAG_CAN_MULTI_CONN_BIT)
 #define NBD_FLAG_SEND_RESIZE       (1 << NBD_FLAG_SEND_RESIZE_BIT)
 #define NBD_FLAG_SEND_CACHE        (1 << NBD_FLAG_SEND_CACHE_BIT)
+#define NBD_FLAG_SEND_FAST_ZERO    (1 << NBD_FLAG_SEND_FAST_ZERO_BIT)
 
 /* New-style handshake (global) flags, sent from server to client, and
    control what will happen during handshake phase. */
@@ -205,6 +207,7 @@ enum {
 #define NBD_CMD_FLAG_DF         (1 << 2) /* don't fragment structured read */
 #define NBD_CMD_FLAG_REQ_ONE    (1 << 3) /* only one extent in BLOCK_STATUS
                                           * reply chunk */
+#define NBD_CMD_FLAG_FAST_ZERO  (1 << 4) /* fail if WRITE_ZEROES is not fast */
 
 /* Supported request types */
 enum {
@@ -270,6 +273,7 @@ static inline bool nbd_reply_type_is_error(int type)
 #define NBD_EINVAL     22
 #define NBD_ENOSPC     28
 #define NBD_EOVERFLOW  75
+#define NBD_ENOTSUP    95
 #define NBD_ESHUTDOWN  108
 
 /* Details collected by NBD_OPT_EXPORT_NAME and NBD_OPT_GO */
diff --git a/nbd/common.c b/nbd/common.c
index cc8b278e54..ddfe7d1183 100644
--- a/nbd/common.c
+++ b/nbd/common.c
@@ -201,6 +201,8 @@ const char *nbd_err_lookup(int err)
         return "ENOSPC";
     case NBD_EOVERFLOW:
         return "EOVERFLOW";
+    case NBD_ENOTSUP:
+        return "ENOTSUP";
     case NBD_ESHUTDOWN:
         return "ESHUTDOWN";
     default:
@@ -231,6 +233,9 @@ int nbd_errno_to_system_errno(int err)
     case NBD_EOVERFLOW:
         ret = EOVERFLOW;
         break;
+    case NBD_ENOTSUP:
+        ret = ENOTSUP;
+        break;
     case NBD_ESHUTDOWN:
         ret = ESHUTDOWN;
         break;
diff --git a/nbd/server.c b/nbd/server.c
index d5078f7468..4992148de1 100644
--- a/nbd/server.c
+++ b/nbd/server.c
@@ -55,6 +55,11 @@ static int system_errno_to_nbd_errno(int err)
         return NBD_ENOSPC;
     case EOVERFLOW:
         return NBD_EOVERFLOW;
+    case ENOTSUP:
+#if ENOTSUP != EOPNOTSUPP
+    case EOPNOTSUPP:
+#endif
+        return NBD_ENOTSUP;
     case ESHUTDOWN:
         return NBD_ESHUTDOWN;
     case EINVAL:
diff --git a/qemu-nbd.c b/qemu-nbd.c
index ae84115076..9032b6de2a 100644
--- a/qemu-nbd.c
+++ b/qemu-nbd.c
@@ -294,6 +294,7 @@ static int qemu_nbd_client_list(SocketAddress *saddr, QCryptoTLSCreds *tls,
                 [NBD_FLAG_CAN_MULTI_CONN_BIT]       = "multi",
                 [NBD_FLAG_SEND_RESIZE_BIT]          = "resize",
                 [NBD_FLAG_SEND_CACHE_BIT]           = "cache",
+                [NBD_FLAG_SEND_FAST_ZERO_BIT]       = "fast-zero",
             };
 
             printf("  size:  %" PRIu64 "\n", list[i].size);