diff --git a/src/backend/commands/dbcommands.c b/src/backend/commands/dbcommands.c
index 91d7481528..9721ce9e0a 100644
--- a/src/backend/commands/dbcommands.c
+++ b/src/backend/commands/dbcommands.c
@@ -123,6 +123,7 @@ createdb(const CreatedbStmt *stmt)
 	const char *dbtemplate = NULL;
 	char	   *dbcollate = NULL;
 	char	   *dbctype = NULL;
+	char	   *canonname;
 	int			encoding = -1;
 	int			dbconnlimit = -1;
 	int			notherbackends;
@@ -318,15 +319,17 @@ createdb(const CreatedbStmt *stmt)
 				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
 				 errmsg("invalid server encoding %d", encoding)));
 
-	/* Check that the chosen locales are valid */
-	if (!check_locale(LC_COLLATE, dbcollate))
+	/* Check that the chosen locales are valid, and get canonical spellings */
+	if (!check_locale(LC_COLLATE, dbcollate, &canonname))
 		ereport(ERROR,
 				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
 				 errmsg("invalid locale name %s", dbcollate)));
-	if (!check_locale(LC_CTYPE, dbctype))
+	dbcollate = canonname;
+	if (!check_locale(LC_CTYPE, dbctype, &canonname))
 		ereport(ERROR,
 				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
 				 errmsg("invalid locale name %s", dbctype)));
+	dbctype = canonname;
 
 	check_encoding_locale_matches(encoding, dbcollate, dbctype);
 
diff --git a/src/backend/utils/adt/pg_locale.c b/src/backend/utils/adt/pg_locale.c
index 9f112e8c5c..0920c13cd9 100644
--- a/src/backend/utils/adt/pg_locale.c
+++ b/src/backend/utils/adt/pg_locale.c
@@ -222,29 +222,43 @@ pg_perm_setlocale(int category, const char *locale)
 
 /*
  * Is the locale name valid for the locale category?
+ *
+ * If successful, and canonname isn't NULL, a palloc'd copy of the locale's
+ * canonical name is stored there.  This is especially useful for figuring out
+ * what locale name "" means (ie, the server environment value).  (Actually,
+ * it seems that on most implementations that's the only thing it's good for;
+ * we could wish that setlocale gave back a canonically spelled version of
+ * the locale name, but typically it doesn't.)
  */
 bool
-check_locale(int category, const char *value)
+check_locale(int category, const char *locale, char **canonname)
 {
 	char	   *save;
-	bool		ret;
+	char	   *res;
+
+	if (canonname)
+		*canonname = NULL;		/* in case of failure */
 
 	save = setlocale(category, NULL);
 	if (!save)
 		return false;			/* won't happen, we hope */
 
-	/* save may be pointing at a modifiable scratch variable, see above */
+	/* save may be pointing at a modifiable scratch variable, see above. */
 	save = pstrdup(save);
 
 	/* set the locale with setlocale, to see if it accepts it. */
-	ret = (setlocale(category, value) != NULL);
+	res = setlocale(category, locale);
+
+	/* save canonical name if requested. */
+	if (res && canonname)
+		*canonname = pstrdup(res);
 
 	/* restore old value. */
 	if (!setlocale(category, save))
-		elog(WARNING, "failed to restore old locale");
+		elog(WARNING, "failed to restore old locale \"%s\"", save);
 	pfree(save);
 
-	return ret;
+	return (res != NULL);
 }
 
 
@@ -262,7 +276,7 @@ check_locale(int category, const char *value)
 bool
 check_locale_monetary(char **newval, void **extra, GucSource source)
 {
-	return check_locale(LC_MONETARY, *newval);
+	return check_locale(LC_MONETARY, *newval, NULL);
 }
 
 void
@@ -274,7 +288,7 @@ assign_locale_monetary(const char *newval, void *extra)
 bool
 check_locale_numeric(char **newval, void **extra, GucSource source)
 {
-	return check_locale(LC_NUMERIC, *newval);
+	return check_locale(LC_NUMERIC, *newval, NULL);
 }
 
 void
@@ -286,7 +300,7 @@ assign_locale_numeric(const char *newval, void *extra)
 bool
 check_locale_time(char **newval, void **extra, GucSource source)
 {
-	return check_locale(LC_TIME, *newval);
+	return check_locale(LC_TIME, *newval, NULL);
 }
 
 void
@@ -322,7 +336,7 @@ check_locale_messages(char **newval, void **extra, GucSource source)
 	 * On Windows, we can't even check the value, so accept blindly
 	 */
 #if defined(LC_MESSAGES) && !defined(WIN32)
-	return check_locale(LC_MESSAGES, *newval);
+	return check_locale(LC_MESSAGES, *newval, NULL);
 #else
 	return true;
 #endif
diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c
index 99cf5b43e9..7a8006e4eb 100644
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -213,7 +213,8 @@ static void trapsig(int signum);
 static void check_ok(void);
 static char *escape_quotes(const char *src);
 static int	locale_date_order(const char *locale);
-static bool check_locale_name(const char *locale);
+static bool check_locale_name(int category, const char *locale,
+							  char **canonname);
 static bool check_locale_encoding(const char *locale, int encoding);
 static void setlocales(void);
 static void usage(const char *progname);
@@ -2240,33 +2241,52 @@ locale_date_order(const char *locale)
 }
 
 /*
- * check if given string is a valid locale specifier
+ * Is the locale name valid for the locale category?
  *
- * this should match the backend check_locale() function
+ * If successful, and canonname isn't NULL, a malloc'd copy of the locale's
+ * canonical name is stored there.  This is especially useful for figuring out
+ * what locale name "" means (ie, the environment value).  (Actually,
+ * it seems that on most implementations that's the only thing it's good for;
+ * we could wish that setlocale gave back a canonically spelled version of
+ * the locale name, but typically it doesn't.)
+ *
+ * this should match the backend's check_locale() function
  */
 static bool
-check_locale_name(const char *locale)
+check_locale_name(int category, const char *locale, char **canonname)
 {
-	bool		ret;
-	int			category = LC_CTYPE;
 	char	   *save;
+	char	   *res;
+
+	if (canonname)
+		*canonname = NULL;		/* in case of failure */
 
 	save = setlocale(category, NULL);
 	if (!save)
-		return false;			/* should not happen; */
+		return false;			/* won't happen, we hope */
 
+	/* save may be pointing at a modifiable scratch variable, so copy it. */
 	save = xstrdup(save);
 
-	ret = (setlocale(category, locale) != NULL);
+	/* set the locale with setlocale, to see if it accepts it. */
+	res = setlocale(category, locale);
 
-	setlocale(category, save);
+	/* save canonical name if requested. */
+	if (res && canonname)
+		*canonname = xstrdup(res);
+
+	/* restore old value. */
+	if (!setlocale(category, save))
+		fprintf(stderr, _("%s: failed to restore old locale \"%s\"\n"),
+				progname, save);
 	free(save);
 
 	/* should we exit here? */
-	if (!ret)
-		fprintf(stderr, _("%s: invalid locale name \"%s\"\n"), progname, locale);
+	if (res == NULL)
+		fprintf(stderr, _("%s: invalid locale name \"%s\"\n"),
+				progname, locale);
 
-	return ret;
+	return (res != NULL);
 }
 
 /*
@@ -2308,11 +2328,13 @@ check_locale_encoding(const char *locale, int user_enc)
 /*
  * set up the locale variables
  *
- * assumes we have called setlocale(LC_ALL,"")
+ * assumes we have called setlocale(LC_ALL, "") -- see set_pglocale_pgservice
  */
 static void
 setlocales(void)
 {
+	char	   *canonname;
+
 	/* set empty lc_* values to locale config if set */
 
 	if (strlen(locale) > 0)
@@ -2332,32 +2354,42 @@ setlocales(void)
 	}
 
 	/*
-	 * override absent/invalid config settings from initdb's locale settings
+	 * canonicalize locale names, and override any missing/invalid values from
+	 * our current environment
 	 */
 
-	if (strlen(lc_ctype) == 0 || !check_locale_name(lc_ctype))
+	if (check_locale_name(LC_CTYPE, lc_ctype, &canonname))
+		lc_ctype = canonname;
+	else
 		lc_ctype = xstrdup(setlocale(LC_CTYPE, NULL));
-	if (strlen(lc_collate) == 0 || !check_locale_name(lc_collate))
+	if (check_locale_name(LC_COLLATE, lc_collate, &canonname))
+		lc_collate = canonname;
+	else
 		lc_collate = xstrdup(setlocale(LC_COLLATE, NULL));
-	if (strlen(lc_numeric) == 0 || !check_locale_name(lc_numeric))
+	if (check_locale_name(LC_NUMERIC, lc_numeric, &canonname))
+		lc_numeric = canonname;
+	else
 		lc_numeric = xstrdup(setlocale(LC_NUMERIC, NULL));
-	if (strlen(lc_time) == 0 || !check_locale_name(lc_time))
+	if (check_locale_name(LC_TIME, lc_time, &canonname))
+		lc_time = canonname;
+	else
 		lc_time = xstrdup(setlocale(LC_TIME, NULL));
-	if (strlen(lc_monetary) == 0 || !check_locale_name(lc_monetary))
+	if (check_locale_name(LC_MONETARY, lc_monetary, &canonname))
+		lc_monetary = canonname;
+	else
 		lc_monetary = xstrdup(setlocale(LC_MONETARY, NULL));
-	if (strlen(lc_messages) == 0 || !check_locale_name(lc_messages))
 #if defined(LC_MESSAGES) && !defined(WIN32)
-	{
-		/* when available get the current locale setting */
+	if (check_locale_name(LC_MESSAGES, lc_messages, &canonname))
+		lc_messages = canonname;
+	else
 		lc_messages = xstrdup(setlocale(LC_MESSAGES, NULL));
-	}
 #else
-	{
-		/* when not available, get the CTYPE setting */
+	/* when LC_MESSAGES is not available, use the LC_CTYPE setting */
+	if (check_locale_name(LC_CTYPE, lc_messages, &canonname))
+		lc_messages = canonname;
+	else
 		lc_messages = xstrdup(setlocale(LC_CTYPE, NULL));
-	}
 #endif
-
 }
 
 #ifdef WIN32
diff --git a/src/include/utils/pg_locale.h b/src/include/utils/pg_locale.h
index 448c01a697..3c38aa2729 100644
--- a/src/include/utils/pg_locale.h
+++ b/src/include/utils/pg_locale.h
@@ -42,7 +42,7 @@ extern void assign_locale_numeric(const char *newval, void *extra);
 extern bool check_locale_time(char **newval, void **extra, GucSource source);
 extern void assign_locale_time(const char *newval, void *extra);
 
-extern bool check_locale(int category, const char *locale);
+extern bool check_locale(int category, const char *locale, char **canonname);
 extern char *pg_perm_setlocale(int category, const char *locale);
 
 extern bool lc_collate_is_c(Oid collation);