diff --git a/include/vfio-user.h b/include/vfio-user.h
index 91d69fc1..a749938c 100644
--- a/include/vfio-user.h
+++ b/include/vfio-user.h
@@ -82,11 +82,11 @@ struct vfio_user_header {
     uint16_t    cmd;
     uint32_t    msg_size;
     uint32_t    flags;
-#define VFIO_USER_F_TYPE         0xf
-#define VFIO_USER_F_TYPE_COMMAND 0x0
-#define VFIO_USER_F_TYPE_REPLY   0x1
-#define VFIO_USER_F_NO_REPLY     0x10
-#define VFIO_USER_F_ERROR        0x20
+#define VFIO_USER_F_TYPE_MASK       (0xf)
+#define VFIO_USER_F_TYPE_COMMAND    (0x0)
+#define VFIO_USER_F_TYPE_REPLY      (0x1)
+#define VFIO_USER_F_NO_REPLY        (0x10)
+#define VFIO_USER_F_ERROR           (0x20)
     uint32_t    error_no;
 } __attribute__((packed));
 
diff --git a/lib/libvfio-user.c b/lib/libvfio-user.c
index 1f886b3d..271a269a 100644
--- a/lib/libvfio-user.c
+++ b/lib/libvfio-user.c
@@ -1283,7 +1283,7 @@ get_request_header(vfu_ctx_t *vfu_ctx, vfu_msg_t **msgp)
 static bool
 is_valid_header(vfu_ctx_t *vfu_ctx, vfu_msg_t *msg)
 {
-    if ((msg->hdr.flags & VFIO_USER_F_TYPE) != VFIO_USER_F_TYPE_COMMAND) {
+    if ((msg->hdr.flags & VFIO_USER_F_TYPE_MASK) != VFIO_USER_F_TYPE_COMMAND) {
         vfu_log(vfu_ctx, LOG_ERR, "msg%#hx: not a command req",
                 msg->hdr.msg_id);
         return false;
diff --git a/lib/tran_pipe.c b/lib/tran_pipe.c
index d1663018..e7aa84d0 100644
--- a/lib/tran_pipe.c
+++ b/lib/tran_pipe.c
@@ -131,7 +131,7 @@ tran_pipe_recv(int fd, struct vfio_user_header *hdr, bool is_reply,
             return ERROR_INT(EPROTO);
         }
 
-        if ((hdr->flags & VFIO_USER_F_TYPE) != VFIO_USER_F_TYPE_REPLY) {
+        if ((hdr->flags & VFIO_USER_F_TYPE_MASK) != VFIO_USER_F_TYPE_REPLY) {
             return ERROR_INT(EINVAL);
         }
 
@@ -142,7 +142,7 @@ tran_pipe_recv(int fd, struct vfio_user_header *hdr, bool is_reply,
             return ERROR_INT(hdr->error_no);
         }
     } else {
-        if ((hdr->flags & VFIO_USER_F_TYPE) != VFIO_USER_F_TYPE_COMMAND) {
+        if ((hdr->flags & VFIO_USER_F_TYPE_MASK) != VFIO_USER_F_TYPE_COMMAND) {
             return ERROR_INT(EINVAL);
         }
         if (msg_id != NULL) {
diff --git a/lib/tran_sock.c b/lib/tran_sock.c
index a737f87d..3f4c8c38 100644
--- a/lib/tran_sock.c
+++ b/lib/tran_sock.c
@@ -211,7 +211,7 @@ tran_sock_recv_fds(int sock, struct vfio_user_header *hdr, bool is_reply,
             return ERROR_INT(EPROTO);
         }
 
-        if ((hdr->flags & VFIO_USER_F_TYPE) != VFIO_USER_F_TYPE_REPLY) {
+        if ((hdr->flags & VFIO_USER_F_TYPE_MASK) != VFIO_USER_F_TYPE_REPLY) {
             return ERROR_INT(EINVAL);
         }
 
@@ -222,7 +222,7 @@ tran_sock_recv_fds(int sock, struct vfio_user_header *hdr, bool is_reply,
             return ERROR_INT(hdr->error_no);
         }
     } else {
-        if ((hdr->flags & VFIO_USER_F_TYPE) != VFIO_USER_F_TYPE_COMMAND) {
+        if ((hdr->flags & VFIO_USER_F_TYPE_MASK) != VFIO_USER_F_TYPE_COMMAND) {
             return ERROR_INT(EINVAL);
         }
         if (msg_id != NULL) {