diff -rupN a/src/backend/commands/collationcmds.c b/src/backend/commands/collationcmds.c
--- a/src/backend/commands/collationcmds.c	2020-11-07 08:03:24.122756440 +0300
+++ b/src/backend/commands/collationcmds.c	2020-11-07 08:04:18.168901199 +0300
@@ -464,7 +464,7 @@ get_icu_language_tag(const char *localen
 	UErrorCode	status;
 
 	status = U_ZERO_ERROR;
-	uloc_toLanguageTag(localename, buf, sizeof(buf), TRUE, &status);
+	uloc_toLanguageTag(localename, buf, sizeof(buf), true, &status);
 	if (U_FAILURE(status))
 		ereport(ERROR,
 				(errmsg("could not convert locale name \"%s\" to language tag: %s",