diff --git a/bin/dig/dig.c b/bin/dig/dig.c
index d31a0b664a..1e724c6185 100644
--- a/bin/dig/dig.c
+++ b/bin/dig/dig.c
@@ -196,6 +196,9 @@ help(void) {
 	       "                 +[no]cmd            (Control display of "
 	       "command line -\n"
 	       "                                      global option)\n"
+	       "                 +[no]coflag         (Set compact denial of "
+	       "existence ok flag)\n"
+	       "                                      in query)\n"
 	       "                 +[no]comments       (Control display of "
 	       "packet "
 	       "header\n"
@@ -1285,6 +1288,11 @@ plus_option(char *option, bool is_batchfile, bool *need_clone,
 			break;
 		case 'o': /* comments */
 			switch (cmd[2]) {
+			case 'f':
+			case '\0': /* +co is a synonym for +coflag */
+				FULLCHECK("coflag");
+				lookup->coflag = state;
+				break;
 			case 'm':
 				FULLCHECK("comments");
 				lookup->comments = state;
diff --git a/bin/dig/dig.rst b/bin/dig/dig.rst
index 59ac9f15dd..88b0a40307 100644
--- a/bin/dig/dig.rst
+++ b/bin/dig/dig.rst
@@ -298,6 +298,13 @@ abbreviation is unambiguous; for example, :option:`+cd` is equivalent to
    always has a global effect; it cannot be set globally and then overridden on a
    per-lookup basis. The default is to print this comment.
 
+.. option:: +coflag, +co, +nocoflag, +noco
+
+   This option sets [or does not set] the CO (Compact denial of
+   existence Ok) EDNS bit in the query.  If set, it tells servers
+   that Compact Denial of Existence responses are acceptable when
+   replying to queries.  The default is ``+nocoflag``.
+
 .. option:: +comments, +nocomments
 
    This option toggles the display of some comment lines in the output, with
@@ -363,7 +370,7 @@ abbreviation is unambiguous; for example, :option:`+cd` is equivalent to
 
    This option sets the must-be-zero EDNS flags bits (Z bits) to the specified value.
    Decimal, hex, and octal encodings are accepted. Setting a named flag
-   (e.g., DO) is silently ignored. By default, no Z bits are set.
+   (e.g. DO, CO) is silently ignored. By default, no Z bits are set.
 
 .. option:: +ednsnegotiation, +noednsnegotiation
 
diff --git a/bin/dig/dighost.c b/bin/dig/dighost.c
index 87fbb41e1c..0f8ac1335c 100644
--- a/bin/dig/dighost.c
+++ b/bin/dig/dighost.c
@@ -789,6 +789,7 @@ clone_lookup(dig_lookup_t *lookold, bool servers) {
 	looknew->aaonly = lookold->aaonly;
 	looknew->adflag = lookold->adflag;
 	looknew->cdflag = lookold->cdflag;
+	looknew->coflag = lookold->coflag;
 	looknew->raflag = lookold->raflag;
 	looknew->tcflag = lookold->tcflag;
 	looknew->print_unknown_format = lookold->print_unknown_format;
@@ -2655,10 +2656,13 @@ setup_lookup(dig_lookup_t *lookup) {
 		}
 
 		flags = lookup->ednsflags;
-		flags &= ~DNS_MESSAGEEXTFLAG_DO;
+		flags &= ~(DNS_MESSAGEEXTFLAG_DO | DNS_MESSAGEEXTFLAG_CO);
 		if (lookup->dnssec) {
 			flags |= DNS_MESSAGEEXTFLAG_DO;
 		}
+		if (lookup->coflag) {
+			flags |= DNS_MESSAGEEXTFLAG_CO;
+		}
 		add_opt(lookup->sendmsg, lookup->udpsize, lookup->edns, flags,
 			opts, i);
 	}
diff --git a/bin/dig/dighost.h b/bin/dig/dighost.h
index 227c315f51..09d136363d 100644
--- a/bin/dig/dighost.h
+++ b/bin/dig/dighost.h
@@ -105,11 +105,10 @@ typedef struct dig_searchlist dig_searchlist_t;
 struct dig_lookup {
 	unsigned int magic;
 	isc_refcount_t references;
-	bool aaonly, adflag, badcookie, besteffort, cdflag, cleared, comments,
-		dns64prefix, dnssec, doing_xfr, done_as_is, ednsneg, expandaaaa,
-		expire, fuzzing, header_only, identify, /*%< Append an "on
-							   server <foo>" message
-							 */
+	bool aaonly, adflag, badcookie, besteffort, cdflag, cleared, coflag,
+		comments, dns64prefix, dnssec, doing_xfr, done_as_is, ednsneg,
+		expandaaaa, expire, fuzzing, header_only,
+		identify, /*%< Append an "on server <foo>" message */
 		identify_previous_line, /*% Prepend a "Nameserver <foo>:"
 					   message, with newline and tab */
 		idnin, idnout, ignore, multiline, need_search, new_search,
diff --git a/lib/dns/include/dns/message.h b/lib/dns/include/dns/message.h
index f15884a183..b4c2c8ee9c 100644
--- a/lib/dns/include/dns/message.h
+++ b/lib/dns/include/dns/message.h
@@ -97,7 +97,8 @@
 #define DNS_MESSAGEFLAG_CD 0x0010U
 
 /*%< EDNS0 extended message flags */
-#define DNS_MESSAGEEXTFLAG_DO 0x8000U
+#define DNS_MESSAGEEXTFLAG_DO 0x8000U /* DNSSEC OK */
+#define DNS_MESSAGEEXTFLAG_CO 0x4000U /* Compact denial of existence OK */
 
 /*%< EDNS0 extended OPT codes */
 #define DNS_OPT_LLQ	      1	 /*%< LLQ opt code */
diff --git a/lib/dns/message.c b/lib/dns/message.c
index 63c07abecb..9fdc2db30e 100644
--- a/lib/dns/message.c
+++ b/lib/dns/message.c
@@ -3513,9 +3513,13 @@ dns_message_pseudosectiontoyaml(dns_message_t *msg, dns_pseudosection_t section,
 		if ((ps->ttl & DNS_MESSAGEEXTFLAG_DO) != 0) {
 			ADD_STRING(target, " do");
 		}
+		if ((ps->ttl & DNS_MESSAGEEXTFLAG_CO) != 0) {
+			ADD_STRING(target, " co");
+		}
 		ADD_STRING(target, "\n");
 		mbz = ps->ttl & 0xffff;
-		mbz &= ~DNS_MESSAGEEXTFLAG_DO; /* Known Flags. */
+		/* Exclude Known Flags. */
+		mbz &= ~(DNS_MESSAGEEXTFLAG_DO | DNS_MESSAGEEXTFLAG_CO);
 		if (mbz != 0) {
 			INDENT(style);
 			ADD_STRING(target, "MBZ: ");
@@ -3871,8 +3875,12 @@ dns_message_pseudosectiontotext(dns_message_t *msg, dns_pseudosection_t section,
 		if ((ps->ttl & DNS_MESSAGEEXTFLAG_DO) != 0) {
 			ADD_STRING(target, " do");
 		}
+		if ((ps->ttl & DNS_MESSAGEEXTFLAG_CO) != 0) {
+			ADD_STRING(target, " co");
+		}
 		mbz = ps->ttl & 0xffff;
-		mbz &= ~DNS_MESSAGEEXTFLAG_DO; /* Known Flags. */
+		/* Exclude Known Flags. */
+		mbz &= ~(DNS_MESSAGEEXTFLAG_DO | DNS_MESSAGEEXTFLAG_CO);
 		if (mbz != 0) {
 			ADD_STRING(target, "; MBZ: ");
 			snprintf(buf, sizeof(buf), "0x%.4x", mbz);