diff --git a/src/runtime/mpz.cpp b/src/runtime/mpz.cpp
index ad8c72df9c..6c451346b9 100644
--- a/src/runtime/mpz.cpp
+++ b/src/runtime/mpz.cpp
@@ -690,7 +690,7 @@ mpz & mpz::operator%=(mpz const & o) {
 
 mpz mpz::pow(unsigned int p) const {
     unsigned mask = 1;
-    mpz power(p);
+    mpz power(*this);
     mpz result(1);
     while (mask <= p) {
         if (mask & p)