diff --git a/src/http/modules/ngx_http_split_clients_module.c b/src/http/modules/ngx_http_split_clients_module.c
index 992f6de..2f92c9e 100644
--- a/src/http/modules/ngx_http_split_clients_module.c
+++ b/src/http/modules/ngx_http_split_clients_module.c
@@ -218,7 +218,7 @@
         part->percent = 0;
 
     } else {
-        if (value[0].data[value[0].len - 1] != '%') {
+        if (value[0].len == 0 || value[0].data[value[0].len - 1] != '%') {
             goto invalid;
         }