diff --git a/sys/geom/part/g_part_gpt.c b/sys/geom/part/g_part_gpt.c
--- a/sys/geom/part/g_part_gpt.c
+++ b/sys/geom/part/g_part_gpt.c
@@ -85,6 +85,7 @@
 	GPT_STATE_MISSING,	/* No signature found. */
 	GPT_STATE_CORRUPT,	/* Checksum mismatch. */
 	GPT_STATE_INVALID,	/* Nonconformant/invalid. */
+	GPT_STATE_UNSUPPORTED,  /* Not supported. */
 	GPT_STATE_OK		/* Perfectly fine. */
 };
 
@@ -148,6 +149,8 @@
 	{ 0, 0 }
 };
 
+#define MAXENTSIZE 1024
+
 static struct g_part_scheme g_part_gpt_scheme = {
 	"GPT",
 	g_part_gpt_methods,
@@ -518,7 +521,11 @@
 	if (lba >= hdr->hdr_lba_start && lba <= hdr->hdr_lba_end)
 		goto fail;
 
-	table->state[elt] = GPT_STATE_OK;
+	if (hdr->hdr_entries > g_part_gpt_scheme.gps_maxent ||
+	    hdr->hdr_entsz > MAXENTSIZE)
+		table->state[elt] = GPT_STATE_UNSUPPORTED;
+	else
+		table->state[elt] = GPT_STATE_OK;
 	le_uuid_dec(&buf->hdr_uuid, &hdr->hdr_uuid);
 	hdr->hdr_crc_table = le32toh(buf->hdr_crc_table);
 
@@ -961,10 +968,19 @@
 	/* Fail if we haven't got any good tables at all. */
 	if (table->state[GPT_ELT_PRITBL] != GPT_STATE_OK &&
 	    table->state[GPT_ELT_SECTBL] != GPT_STATE_OK) {
-		printf("GEOM: %s: corrupt or invalid GPT detected.\n",
-		    pp->name);
-		printf("GEOM: %s: GPT rejected -- may not be recoverable.\n",
-		    pp->name);
+		/* XXX arbitrarily report unsupported as the table is not checked */
+		if (table->state[GPT_ELT_PRIHDR] == GPT_STATE_UNSUPPORTED &&
+		    table->state[GPT_ELT_SECHDR] == GPT_STATE_UNSUPPORTED &&
+		    gpt_matched_hdrs(prihdr, sechdr)) {
+			printf("GEOM: %s: unsupported GPT detected.\n",
+			    pp->name);
+			printf("GEOM: %s: GPT rejected.\n", pp->name);
+		} else {
+			printf("GEOM: %s: corrupt or invalid GPT detected.\n",
+			    pp->name);
+			printf("GEOM: %s: GPT rejected -- may not be recoverable.\n",
+			    pp->name);
+		}
 		if (prihdr != NULL)
 			g_free(prihdr);
 		if (pritbl != NULL)