diff --git a/sys/amd64/amd64/db_disasm.c b/sys/amd64/amd64/db_disasm.c
index 0ec81f47fd44..ea411f7b4683 100644
--- a/sys/amd64/amd64/db_disasm.c
+++ b/sys/amd64/amd64/db_disasm.c
@@ -145,6 +145,26 @@ static const struct inst db_inst_0f388x[] = {
 /*8f*/	{ "",	   FALSE, NONE,  0,	      0 },
 };
 
+static const struct inst db_inst_0f38fx[] = {
+/*f0*/	{ "crc32b",TRUE,  NONE,  op2(Eb, R),  0 },
+/*f1*/	{ "crc32", TRUE,  LONG,  op2(E, R),   0 },
+/*f2*/	{ "",	   FALSE, NONE,  0,	      0 },
+/*f3*/	{ "",	   FALSE, NONE,  0,	      0 },
+/*f4*/	{ "",	   FALSE, NONE,  0,	      0 },
+/*f5*/	{ "",	   FALSE, NONE,  0,	      0 },
+/*f6*/	{ "",	   FALSE, NONE,  0,	      0 },
+/*f7*/	{ "",	   FALSE, NONE,  0,	      0 },
+
+/*f8*/	{ "",	   FALSE, NONE,  0,	      0 },
+/*f9*/	{ "",	   FALSE, NONE,  0,	      0 },
+/*fa*/	{ "",	   FALSE, NONE,  0,	      0 },
+/*fb*/	{ "",	   FALSE, NONE,  0,	      0 },
+/*fc*/	{ "",	   FALSE, NONE,  0,	      0 },
+/*fd*/	{ "",	   FALSE, NONE,  0,	      0 },
+/*fe*/	{ "",	   FALSE, NONE,  0,	      0 },
+/*ff*/	{ "",	   FALSE, NONE,  0,	      0 },
+};
+
 static const struct inst * const db_inst_0f38[] = {
 	0,
 	0,
@@ -161,7 +181,7 @@ static const struct inst * const db_inst_0f38[] = {
 	0,
 	0,
 	0,
-	0
+	db_inst_0f38fx
 };
 
 static const char * const db_Grp6[] = {
@@ -1238,7 +1258,7 @@ db_disasm(db_addr_t loc, bool altfmt)
 	boolean_t	first;
 	int	displ;
 	int	prefix;
-	int	rep;
+	int	rep, repne;
 	int	imm;
 	int	imm2;
 	long	imm64;
@@ -1254,6 +1274,7 @@ db_disasm(db_addr_t loc, bool altfmt)
 	 * Get prefixes
 	 */
 	rep = FALSE;
+	repne = FALSE;
 	prefix = TRUE;
 	do {
 	    switch (inst) {
@@ -1284,8 +1305,12 @@ db_disasm(db_addr_t loc, bool altfmt)
 		case 0xf0:
 		    db_printf("lock ");
 		    break;
+		    /*
+		     * XXX repne/repe are only actually valid for MOVS, CMPS,
+		     * SCAS, LODS, STOS, INS, OUTS.
+		     */
 		case 0xf2:
-		    db_printf("repne ");
+		    repne = TRUE;
 		    break;
 		case 0xf3:
 		    rep = TRUE;
@@ -1480,6 +1505,11 @@ db_disasm(db_addr_t loc, bool altfmt)
 		rep = FALSE;
 	    }
 	}
+	/* N.B., likely highly incomplete. */
+	if (repne) {
+		if (ip == &db_inst_0f38fx[0] || ip == &db_inst_0f38fx[1])
+			repne = FALSE;
+	}
 	if (size == WORD) {
 	    if (ip->i_extra == db_Grp9 && f_mod(rex, regmodrm) != 3 &&
 		f_reg(rex, regmodrm) == 0x6) {
@@ -1495,6 +1525,8 @@ db_disasm(db_addr_t loc, bool altfmt)
 
 	if (rep == TRUE)
 	    db_printf("repe ");	/* XXX repe VS rep */
+	if (repne == TRUE)
+	    db_printf("repne ");
 
 	if (i_size == SDEP) {
 	    if (size == LONG)