diff --git a/lib/telnet.c b/lib/telnet.c
index 6915e601d..aea4fdd82 100644
--- a/lib/telnet.c
+++ b/lib/telnet.c
@@ -878,7 +878,7 @@ static void suboption(struct connectdata *conn)
         tmplen = (strlen(v->data) + 1);
         /* Add the variable only if it fits */
         if(len + tmplen < (int)sizeof(temp)-6) {
-          sscanf(v->data, "%127[^,],%s", varname, varval);
+          sscanf(v->data, "%127[^,],%127s", varname, varval);
           snprintf((char *)&temp[len], sizeof(temp) - len,
                    "%c%s%c%s", CURL_NEW_ENV_VAR, varname,
                    CURL_NEW_ENV_VALUE, varval);