--- JSON-XS/XS.xs	2019/03/06 07:32:06	1.139
+++ JSON-XS/XS.xs	2019/04/19 17:09:51	1.140
@@ -164,7 +164,7 @@
 }
 
 /* adds two STRLENs together, slow, and with paranoia */
-STRLEN
+static STRLEN
 strlen_sum (STRLEN l1, STRLEN l2)
 {
   size_t sum = l1 + l2;