diff --git a/bin/dig/dighost.c b/bin/dig/dighost.c
index da87423d6f..fd4c7389ff 100644
--- a/bin/dig/dighost.c
+++ b/bin/dig/dighost.c
@@ -22,15 +22,12 @@
 #include <errno.h>
 #include <inttypes.h>
 #include <limits.h>
+#include <locale.h>
 #include <stdbool.h>
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
 
-#ifdef HAVE_LOCALE_H
-#include <locale.h>
-#endif /* ifdef HAVE_LOCALE_H */
-
 #ifdef HAVE_LIBIDN2
 #include <idn2.h>
 #endif /* HAVE_LIBIDN2 */
@@ -91,6 +88,9 @@
 #include <pk11/result.h>
 #endif /* if USE_PKCS11 */
 
+#define systemlocale(l) (void)setlocale(l, "")
+#define resetlocale(l)	(void)setlocale(l, "C")
+
 dig_lookuplist_t lookup_list;
 dig_serverlist_t server_list;
 dig_searchlistlist_t search_list;
@@ -1295,11 +1295,6 @@ setup_system(bool ipv4only, bool ipv6only) {
 
 	irs_resconf_destroy(&resconf);
 
-#ifdef HAVE_SETLOCALE
-	/* Set locale */
-	(void)setlocale(LC_ALL, "");
-#endif /* ifdef HAVE_SETLOCALE */
-
 	if (keyfile[0] != 0) {
 		setup_file_key();
 	} else if (keysecret[0] != 0) {
@@ -4288,8 +4283,9 @@ destroy_libs(void) {
 #ifdef HAVE_LIBIDN2
 static isc_result_t
 idn_output_filter(isc_buffer_t *buffer, unsigned int used_org) {
-	char src[MXNAME], *dst;
+	char src[MXNAME], *dst = NULL;
 	size_t srclen, dstlen;
+	isc_result_t result = ISC_R_SUCCESS;
 
 	/*
 	 * Copy name from 'buffer' to 'src' and terminate it with NULL.
@@ -4297,23 +4293,27 @@ idn_output_filter(isc_buffer_t *buffer, unsigned int used_org) {
 	srclen = isc_buffer_usedlength(buffer) - used_org;
 	if (srclen >= sizeof(src)) {
 		warn("Input name too long to perform IDN conversion");
-		return (ISC_R_SUCCESS);
+		goto cleanup;
 	}
 	memmove(src, (char *)isc_buffer_base(buffer) + used_org, srclen);
 	src[srclen] = '\0';
 
+	systemlocale(LC_ALL);
+
 	/*
 	 * Convert 'src' to the current locale's character encoding.
 	 */
 	idn_ace_to_locale(src, &dst);
 
+	resetlocale(LC_ALL);
+
 	/*
 	 * Check whether the converted name will fit back into 'buffer'.
 	 */
 	dstlen = strlen(dst);
 	if (isc_buffer_length(buffer) < used_org + dstlen) {
-		idn2_free(dst);
-		return (ISC_R_NOSPACE);
+		result = ISC_R_NOSPACE;
+		goto cleanup;
 	}
 
 	/*
@@ -4326,9 +4326,12 @@ idn_output_filter(isc_buffer_t *buffer, unsigned int used_org) {
 	/*
 	 * Clean up.
 	 */
-	idn2_free(dst);
+cleanup:
+	if (dst != NULL) {
+		idn2_free(dst);
+	}
 
-	return (ISC_R_SUCCESS);
+	return (result);
 }
 
 /*%
@@ -4344,6 +4347,8 @@ idn_locale_to_ace(const char *src, char *dst, size_t dstlen) {
 	char *ascii_src;
 	int res;
 
+	systemlocale(LC_ALL);
+
 	/*
 	 * We trust libidn2 to return an error if 'src' is too large to be a
 	 * valid domain name.
@@ -4364,6 +4369,8 @@ idn_locale_to_ace(const char *src, char *dst, size_t dstlen) {
 	(void)strlcpy(dst, final_src, dstlen);
 
 	idn2_free(ascii_src);
+
+	resetlocale(LC_ALL);
 }
 
 /*%
@@ -4378,6 +4385,8 @@ idn_ace_to_locale(const char *src, char **dst) {
 	char *local_src, *utf8_src;
 	int res;
 
+	systemlocale(LC_ALL);
+
 	/*
 	 * We need to:
 	 *
@@ -4443,6 +4452,8 @@ idn_ace_to_locale(const char *src, char **dst) {
 	idn2_free(utf8_src);
 
 	*dst = local_src;
+
+	resetlocale(LC_ALL);
 }
 #endif /* HAVE_LIBIDN2 */
 
diff --git a/bin/dig/host.c b/bin/dig/host.c
index ba0bbe63d0..602d7a61c2 100644
--- a/bin/dig/host.c
+++ b/bin/dig/host.c
@@ -13,13 +13,10 @@
 
 #include <inttypes.h>
 #include <limits.h>
+#include <locale.h>
 #include <stdbool.h>
 #include <stdlib.h>
 
-#ifdef HAVE_LOCALE_H
-#include <locale.h>
-#endif /* ifdef HAVE_LOCALE_H */
-
 #include <isc/app.h>
 #include <isc/attributes.h>
 #include <isc/commandline.h>
diff --git a/bin/named/main.c b/bin/named/main.c
index 46f4b57a9c..a513fc61ae 100644
--- a/bin/named/main.c
+++ b/bin/named/main.c
@@ -13,6 +13,7 @@
 
 #include <ctype.h>
 #include <inttypes.h>
+#include <locale.h>
 #include <stdbool.h>
 #include <stdlib.h>
 #include <string.h>
@@ -1423,6 +1424,18 @@ main(int argc, char *argv[]) {
 	xmlInitThreads();
 #endif /* HAVE_LIBXML2 */
 
+	/*
+	 * Technically, this call is superfluous because on startup of the main
+	 * program, the portable "C" locale is selected by default.  This
+	 * explicit call here is for a reference that the BIND 9 code base is
+	 * not locale aware and the locale MUST be set to "C" (or "POSIX") when
+	 * calling any BIND 9 library code.  If you are calling external
+	 * libraries that use locale, such calls must be wrapped into
+	 * setlocale(LC_ALL, ""); before the call and setlocale(LC_ALL, "C");
+	 * after the call, and no BIND 9 library calls must be made in between.
+	 */
+	setlocale(LC_ALL, "C");
+
 	/*
 	 * Record version in core image.
 	 * strings named.core | grep "named version:"
diff --git a/configure.ac b/configure.ac
index 4f05966753..f1b3ac0b2c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1363,12 +1363,6 @@ AC_SUBST([CMOCKA_LIBS])
 
 AM_CONDITIONAL([HAVE_CMOCKA], [test "$with_cmocka" = "yes"])
 
-#
-# Check for i18n
-#
-AC_CHECK_HEADERS(locale.h)
-AC_CHECK_FUNCS(setlocale)
-
 #
 # was --with-tuning specified?
 #