diff --git a/stage0/src/runtime/compact.cpp b/stage0/src/runtime/compact.cpp
index fe4e8be044..1d899fd155 100644
--- a/stage0/src/runtime/compact.cpp
+++ b/stage0/src/runtime/compact.cpp
@@ -274,11 +274,11 @@ void object_compactor::insert_mpz(object * o) {
     size_t data_sz = sizeof(mpn_digit) * to_mpz(o)->m_value.m_size;
     size_t sz      = sizeof(mpz_object) + data_sz;
     mpz_object * new_o = (mpz_object *)alloc(sz);
+    memcpy(new_o, to_mpz(o), sizeof(mpz_object));
     lean_set_non_heap_header((lean_object*)new_o, sz, LeanMPZ, 0);
-    new_o->m_value.m_size   = to_mpz(o)->m_value.m_size;
-    new_o->m_value.m_sign   = to_mpz(o)->m_value.m_sign;
-    new_o->m_value.m_digits = reinterpret_cast<mpn_digit*>(reinterpret_cast<char*>(new_o) + sizeof(mpz_object));
-    memcpy(new_o->m_value.m_digits, to_mpz(o)->m_value.m_digits, data_sz);
+    void * data = reinterpret_cast<char*>(new_o) + sizeof(mpz_object);
+    memcpy(data, to_mpz(o)->m_value.m_digits, data_sz);
+    new_o->m_value.m_digits = reinterpret_cast<mpn_digit *>(reinterpret_cast<char *>(data) - reinterpret_cast<char *>(m_begin) + reinterpret_cast<ptrdiff_t>(m_base_addr));
     save(o, (lean_object*)new_o);
 #endif
 }
diff --git a/stage0/src/util/shell.cpp b/stage0/src/util/shell.cpp
index 6709d9f21d..0a9a987128 100644
--- a/stage0/src/util/shell.cpp
+++ b/stage0/src/util/shell.cpp
@@ -64,7 +64,7 @@ Author: Leonardo de Moura
 enum arg_opt { no_argument, required_argument, optional_argument };
 
 struct option {
-    const char name[12];
+    const char name[20];
     arg_opt has_arg;
     int *flag;
     char val;