diff --git a/Firmware/ultralcd.cpp b/Firmware/ultralcd.cpp
index c0fa36887..13ee04275 100755
--- a/Firmware/ultralcd.cpp
+++ b/Firmware/ultralcd.cpp
@@ -8974,7 +8974,7 @@ bool FarmOrUserECool(){
 
 #ifdef PRUSA_SN_SUPPORT
 void WorkaroundPrusaSN() {
-    const char *SN = PSTR("CZPX000000000000000");
+    const char *SN = PSTR("CZPXInvalidSerialNr");
     for (uint8_t i = 0; i < 20; i++) {
         eeprom_update_byte((uint8_t*)EEPROM_PRUSA_SN + i, pgm_read_byte(SN++));
     }