No, that risk always existed. When the Communists took over Russia, they did not bother to honor all of the Tsarist debts. A country is not like a company. Sovereign default is always a choice. That is what it means to be sovereign.

There have been over 70 incidents of overt domestic default since 1800. The United States defaulted in 1790, when a portion of the interest it owed was deferred for 10 years, and technically defaulted again in 1933 when it abrogated the gold clause.