diff --git a/src/machine.cpp b/src/machine.cpp
index 44a131db2d..e47d5ffbc5 100644
--- a/src/machine.cpp
+++ b/src/machine.cpp
@@ -974,6 +974,8 @@ getClassAddendum(Thread* t, object class_, object pool)
 {
   object addendum = classAddendum(t, class_);
   if (addendum == 0) {
+    PROTECT(t, class_);
+
     addendum = makeClassAddendum(t, pool, 0, 0, 0, 0, 0);
     set(t, class_, ClassAddendum, addendum);
   }
@@ -1879,6 +1881,8 @@ makeArrayClass(Thread* t, object loader, unsigned dimensions, object spec,
      loader,
      arrayLength(t, vtable));
 
+  PROTECT(t, c);
+
   t->m->processor->initVtable(t, c);
 
   return c;