diff --git a/src/util/mpq.h b/src/util/mpq.h
index eef06e2ae..90a01530b 100644
--- a/src/util/mpq.h
+++ b/src/util/mpq.h
@@ -31,6 +31,7 @@ public:
     mpq():m_den(1) {}
     mpq(mpq &&) noexcept = default;
     mpq & operator=(mpq const &) = delete;
+    mpq & operator=(mpq&&) = delete;
     void swap(mpq & other) { m_num.swap(other.m_num); m_den.swap(other.m_den); }
     mpz const & numerator() const { return m_num; }
     mpz const & denominator() const { return m_den; }