diff --git a/hw/cxl/cxl-cdat.c b/hw/cxl/cxl-cdat.c
index 24829cf242..2fea975671 100644
--- a/hw/cxl/cxl-cdat.c
+++ b/hw/cxl/cxl-cdat.c
@@ -49,6 +49,7 @@ static void ct3_build_cdat(CDATObject *cdat, Error **errp)
     g_autofree CDATTableHeader *cdat_header = NULL;
     g_autofree CDATEntry *cdat_st = NULL;
     uint8_t sum = 0;
+    uint8_t *hdr_buf;
     int ent, i;
 
     /* Use default table if fopen == NULL */
@@ -95,8 +96,12 @@ static void ct3_build_cdat(CDATObject *cdat, Error **errp)
     /* For now, no runtime updates */
     cdat_header->sequence = 0;
     cdat_header->length += sizeof(CDATTableHeader);
-    sum += cdat_header->revision + cdat_header->sequence +
-        cdat_header->length;
+
+    hdr_buf = (uint8_t *)cdat_header;
+    for (i = 0; i < sizeof(*cdat_header); i++) {
+        sum += hdr_buf[i];
+    }
+
     /* Sum of all bytes including checksum must be 0 */
     cdat_header->checksum = ~sum + 1;