diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c
index bae97539fc8..0acfd0fea29 100644
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -2243,46 +2243,44 @@ check_icu_locale_encoding(int user_enc)
 }
 
 /*
- * Check that ICU accepts the locale name; or if not specified, retrieve the
- * default ICU locale.
+ * Determine default ICU locale by opening the default collator and reading
+ * its locale.
+ *
+ * NB: The default collator (opened using NULL) is different from the collator
+ * for the root locale (opened with "", "und", or "root"). The former depends
+ * on the environment (useful at initdb time) and the latter does not.
  */
-static void
-check_icu_locale(void)
+static char *
+default_icu_locale(void)
 {
 #ifdef USE_ICU
 	UCollator	*collator;
 	UErrorCode   status;
+	const char	*valid_locale;
+	char		*default_locale;
 
 	status = U_ZERO_ERROR;
-	collator = ucol_open(icu_locale, &status);
+	collator = ucol_open(NULL, &status);
+	if (U_FAILURE(status))
+		pg_fatal("could not open collator for default locale: %s",
+				 u_errorName(status));
+
+	status = U_ZERO_ERROR;
+	valid_locale = ucol_getLocaleByType(collator, ULOC_VALID_LOCALE,
+										&status);
 	if (U_FAILURE(status))
 	{
-		if (icu_locale)
-			pg_fatal("could not open collator for locale \"%s\": %s",
-					 icu_locale, u_errorName(status));
-		else
-			pg_fatal("could not open collator for default locale: %s",
-					 u_errorName(status));
+		ucol_close(collator);
+		pg_fatal("could not determine default ICU locale");
 	}
 
-	/* if not specified, get locale from default collator */
-	if (icu_locale == NULL)
-	{
-		const char	*default_locale;
-
-		status = U_ZERO_ERROR;
-		default_locale = ucol_getLocaleByType(collator, ULOC_VALID_LOCALE,
-											  &status);
-		if (U_FAILURE(status))
-		{
-			ucol_close(collator);
-			pg_fatal("could not determine default ICU locale");
-		}
-
-		icu_locale = pg_strdup(default_locale);
-	}
+	default_locale = pg_strdup(valid_locale);
 
 	ucol_close(collator);
+
+	return default_locale;
+#else
+	pg_fatal("ICU is not supported in this build");
 #endif
 }
 
@@ -2339,7 +2337,9 @@ setlocales(void)
 
 	if (locale_provider == COLLPROVIDER_ICU)
 	{
-		check_icu_locale();
+		/* acquire default locale from the environment, if not specified */
+		if (icu_locale == NULL)
+			icu_locale = default_icu_locale();
 
 		/*
 		 * In supported builds, the ICU locale ID will be checked by the