diff --git a/src/utils.cpp b/src/utils.cpp
index 830783f..45dbae0 100644
--- a/src/utils.cpp
+++ b/src/utils.cpp
@@ -402,6 +402,7 @@ namespace Utils {
             cleanCallsign = callsign.substring(0, callsign.indexOf("-"));
             String ssid = callsign.substring(callsign.indexOf("-") + 1);
             if (ssid.indexOf("-") != -1 || ssid.length() > 2) return false;
+            if (ssid.length() == 2 && ssid[0] == '0') return false;
             for (int i = 0; i < ssid.length(); i++) {
                 if (!isAlphaNumeric(ssid[i])) return false;
             }