diff --git a/ampel-firmware/src/lib/IotWebConf/src/IotWebConfTParameter.h b/ampel-firmware/src/lib/IotWebConf/src/IotWebConfTParameter.h
index ecf50c801917c9cfe91ac9983265e813d10629c3..63934115b4ebe5c5ddbe3230039c40598877c139 100644
--- a/ampel-firmware/src/lib/IotWebConf/src/IotWebConfTParameter.h
+++ b/ampel-firmware/src/lib/IotWebConf/src/IotWebConfTParameter.h
@@ -419,7 +419,7 @@ protected:
     if (length > 0)
     {
       char parLength[11];
-      snprintf(parLength, 11, "%d", length);
+      snprintf(parLength, 11, "%d", length - 1); // To allow "\0" at the end of the string.
       String maxLength = String("maxlength=") + parLength;
       pitem.replace("{l}", maxLength);
     }