diff --git a/src/backend/utils/adt/varlena.c b/src/backend/utils/adt/varlena.c
index a0dd391..d24d1c5 100644
--- a/src/backend/utils/adt/varlena.c
+++ b/src/backend/utils/adt/varlena.c
@@ -1433,7 +1433,8 @@ varstr_cmp(char *arg1, int len1, char *arg2, int len2, Oid collid)
 
 #ifdef WIN32
 		/* Win32 does not have UTF-8, so we need to map to UTF-16 */
-		if (GetDatabaseEncoding() == PG_UTF8)
+		if (GetDatabaseEncoding() == PG_UTF8 &&
+			(!mylocale || mylocale->provider == COLLPROVIDER_LIBC))
 		{
 			int			a1len;
 			int			a2len;