diff --git a/armsrc/sam_picopass.c b/armsrc/sam_picopass.c
index ad801b1f4..1504f4104 100644
--- a/armsrc/sam_picopass.c
+++ b/armsrc/sam_picopass.c
@@ -239,7 +239,7 @@ static int sam_send_request_iso15(const uint8_t *const request, const uint8_t re
     }
 
     if (sam_rx_buf[6] == 0x81 && sam_rx_buf[8] == 0x8a && sam_rx_buf[9] == 0x81 ){ //check if the response is an SNMP message
-        *response_len = sam_rx_buf[6 + 1] + 3;
+        *response_len = sam_rx_buf[5 + 2] + 3;
     }else{ //if not, use the old logic
         *response_len = sam_rx_buf[5 + 1] + 2;
     }