diff --git a/src/context.c b/src/context.c
index 847fb041..37f056bf 100644
--- a/src/context.c
+++ b/src/context.c
@@ -1309,6 +1309,7 @@ getdns_context_create_with_extended_memory_functions(
 	result->header = NULL;
 	result->add_opt_parameters = NULL;
 	result->add_warning_for_bad_dns = 0;
+	result->dns64 = 0;
 	result->dnssec_return_all_statuses = 0;
 	result->dnssec_return_full_validation_chain = 0;
 	result->dnssec_return_only_secure = 0;
@@ -1321,6 +1322,7 @@ getdns_context_create_with_extended_memory_functions(
 	result->return_api_information = 0;
 	result->return_both_v4_and_v6 = 0;
 	result->return_call_reporting = 0;
+	(void) memset(result->dns64_prefix, 0, 16);
 	result->specify_class = GETDNS_RRCLASS_IN;
 
 	/* state data used to detect changes to the system config files
@@ -4036,6 +4038,7 @@ _getdns_context_config_setting(getdns_context *context,
 	getdns_return_t r = GETDNS_RETURN_GOOD;
 	getdns_dict *dict;
 	getdns_list *list;
+	getdns_bindata *bindata;
 	getdns_namespace_t namespaces[100];
 	getdns_transport_list_t dns_transport_list[100];
 	size_t count, i;
@@ -4081,6 +4084,7 @@ _getdns_context_config_setting(getdns_context *context,
 	/****                              ****/
 	/**************************************/
 	EXTENSION_SETTING_BOOL(add_warning_for_bad_dns)
+	EXTENSION_SETTING_BOOL(dns64)
 	EXTENSION_SETTING_BOOL(dnssec_return_all_statuses)
 	EXTENSION_SETTING_BOOL(dnssec_return_full_validation_chain)
 	EXTENSION_SETTING_BOOL(dnssec_return_only_secure)
@@ -4097,13 +4101,25 @@ _getdns_context_config_setting(getdns_context *context,
 	EXTENSION_SETTING_BOOL(return_call_reporting)
 
 	} else if (_streq(setting, "add_opt_parameters")) {
-		if (!(r = getdns_dict_get_dict(config_dict, "add_opt_parameters" , &dict))) {
+		if (!(r = getdns_dict_get_dict(config_dict,
+		    "add_opt_parameters", &dict))) {
 			if (context->add_opt_parameters)
-				getdns_dict_destroy(context->add_opt_parameters);
+				getdns_dict_destroy(
+				    context->add_opt_parameters);
 			context->add_opt_parameters = NULL;
-			r = _getdns_dict_copy(dict, &context->add_opt_parameters);
+			r = _getdns_dict_copy(
+			    dict, &context->add_opt_parameters);
 		}
 
+	} else if (_streq(setting, "dns64_prefix")) {
+		if (!(r = getdns_dict_get_bindata(config_dict, "dns64_prefix",
+		    &bindata))) {
+			if (bindata->size != 16)
+				r = GETDNS_RETURN_NO_SUCH_LIST_ITEM;
+			else
+				(void) memcpy(context->dns64_prefix,
+				    bindata->data, 16);
+		}
 	} else if (_streq(setting, "header")) {
 		if (!(r = getdns_dict_get_dict(config_dict, "header" , &dict))) {
 			if (context->header)
diff --git a/src/context.h b/src/context.h
index 84a2c40c..c6288965 100644
--- a/src/context.h
+++ b/src/context.h
@@ -301,6 +301,7 @@ struct getdns_context {
 	getdns_dict *header;
 	getdns_dict *add_opt_parameters;
 	int add_warning_for_bad_dns             : 1;
+	int dns64                               : 1;
 	int dnssec_return_all_statuses          : 1;
 	int dnssec_return_full_validation_chain : 1;
 	int dnssec_return_only_secure           : 1;
@@ -314,6 +315,7 @@ struct getdns_context {
 	int return_both_v4_and_v6               : 1;
 	int return_call_reporting               : 1;
 	uint16_t specify_class;
+	uint8_t dns64_prefix[16];
 
 	/*
 	 * state data used to detect changes to the system config files
diff --git a/src/general.c b/src/general.c
index 99e4cff5..882a0ba2 100644
--- a/src/general.c
+++ b/src/general.c
@@ -360,6 +360,8 @@ validate_extensions(struct getdns_dict * extensions)
 	static getdns_extension_format extformats[] = {
 		{"add_opt_parameters"            , t_dict, 1},
 		{"add_warning_for_bad_dns"       , t_int , 1},
+		{"dns64"                         , t_int , 1},
+		{"dns64_prefix"                  , t_bindata, 1},
 		{"dnssec_return_all_statuses"    , t_int , 1},
 		{"dnssec_return_full_validation_chain", t_int , 1},
 		{"dnssec_return_only_secure"     , t_int , 1},
diff --git a/src/request-internal.c b/src/request-internal.c
index 141f977a..66e14656 100644
--- a/src/request-internal.c
+++ b/src/request-internal.c
@@ -720,6 +720,7 @@ _getdns_dns_req_new(getdns_context *context, getdns_eventloop *loop,
 
 	getdns_dns_req *result = NULL;
         uint32_t klass = context->specify_class;
+	getdns_bindata *dns64_prefix = NULL;
 	int a_aaaa_query = is_extension_set(extensions,
 	    "return_both_v4_and_v6", context->return_both_v4_and_v6) &&
 	    ( request_type == GETDNS_RRTYPE_A ||
@@ -908,6 +909,12 @@ _getdns_dns_req_new(getdns_context *context, getdns_eventloop *loop,
 	    "return_call_reporting"  , context->return_call_reporting);
 	result->add_warning_for_bad_dns        = is_extension_set(extensions,
 	    "add_warning_for_bad_dns", context->add_warning_for_bad_dns);
+
+	result->dns64 = is_extension_set(extensions, "dns64", context->dns64);
+	if (!getdns_dict_get_bindata(extensions, "dns64_prefix", &dns64_prefix)
+	    && dns64_prefix->size == 16)
+		(void) memcpy(result->dns64_prefix, dns64_prefix->data, 16);
+	else	(void) memcpy(result->dns64_prefix, context->dns64_prefix, 16);
 	
 	/* will be set by caller */
 	result->user_pointer = NULL;
diff --git a/src/tools/getdns_query.c b/src/tools/getdns_query.c
index 7acc77d9..f5d19fc3 100644
--- a/src/tools/getdns_query.c
+++ b/src/tools/getdns_query.c
@@ -164,6 +164,8 @@ print_usage(FILE *out, const char *progname)
 	fprintf(out, "\ntsig spec: [<algorithm>:]<name>:<secret in Base64>\n");
 	fprintf(out, "\nextensions:\n");
 	fprintf(out, "\t+add_warning_for_bad_dns\n");
+	fprintf(out, "\t+dns64\n");
+	fprintf(out, "\t+dns64_prefix=<ipv6 prefix>\n");
 	fprintf(out, "\t+dnssec_return_status\n");
 	fprintf(out, "\t+dnssec_return_only_secure\n");
 	fprintf(out, "\t+dnssec_return_all_statuses\n");
@@ -477,10 +479,10 @@ getdns_return_t parse_args(int argc, char **argv)
 	int t, print_api_info = 0, print_trust_anchors = 0;
 	getdns_list *upstream_list = NULL;
 	getdns_list *tas = NULL, *hints = NULL;
-	getdns_dict *pubkey_pin = NULL;
+	getdns_dict *pubkey_pin = NULL, *addr_dict;
 	getdns_list *suffixes;
 	char *suffix;
-	getdns_bindata bindata;
+	getdns_bindata bindata, *address;
 	size_t upstream_count = 0;
 	FILE *fh;
 	char *config_file = NULL;
@@ -508,6 +510,14 @@ getdns_return_t parse_args(int argc, char **argv)
 					fprintf(stderr,
 					    "Unknown class: %s\n", arg+15);
 
+			} else if (strncmp(arg+1, "dns64_prefix=", 13) == 0) {
+				if (!(r = getdns_str2dict(arg+14, &addr_dict))
+				    && !(r = getdns_dict_get_bindata(
+				    addr_dict, "address_data", &address))) {
+					r = getdns_dict_set_bindata(extensions,
+					    "dns64_prefix", address);
+					getdns_dict_destroy(addr_dict);
+				}
 			} else if (arg[1] == '0') {
 			    /* Unset all existing extensions*/
 				getdns_dict_destroy(extensions);
diff --git a/src/types-internal.h b/src/types-internal.h
index f6c3cf5b..1ccadcf4 100644
--- a/src/types-internal.h
+++ b/src/types-internal.h
@@ -289,6 +289,7 @@ typedef struct getdns_dns_req {
 	int canceled				: 1;
 
 	/* request extensions */
+	int dns64                               : 1;
 	int dnssec_return_status		: 1;
 	int dnssec_return_only_secure		: 1;
 	int dnssec_return_all_statuses		: 1;
@@ -318,6 +319,8 @@ typedef struct getdns_dns_req {
 	int validating                          : 1;
 	int *freed;
 
+	/* Non boolean request extensions */
+	uint8_t dns64_prefix[16];
 	uint16_t tls_query_padding_blocksize;
 
 	/* internally scheduled request */