diff --git a/vm/data_heap.cpp b/vm/data_heap.cpp
index 9791c33892..e13d0dbae1 100755
--- a/vm/data_heap.cpp
+++ b/vm/data_heap.cpp
@@ -245,10 +245,14 @@ cell factor_vm::instances(cell type)
 	each_object(accum);
 	cell object_count = accum.objects.size();
 
-	gc_off = true;
+	data_roots.push_back(accum.objects[0]);
+	data_roots.push_back(object_count);
+
 	array *objects = allot_array(object_count,false_object);
 	memcpy(objects->data(),&accum.objects[0],object_count * sizeof(cell));
-	gc_off = false;
+
+	data_roots.pop_back();
+	data_roots.pop_back();
 
 	return tag<array>(objects);
 }
diff --git a/vm/data_roots.hpp b/vm/data_roots.hpp
index 52654c49f0..1b3eb888ef 100644
--- a/vm/data_roots.hpp
+++ b/vm/data_roots.hpp
@@ -8,6 +8,7 @@ struct data_root : public tagged<Type> {
 	void push()
 	{
 		parent->data_roots.push_back((cell)this);
+		parent->data_roots.push_back(1);
 	}
 
 	explicit data_root(cell value_, factor_vm *parent_)
@@ -27,6 +28,10 @@ struct data_root : public tagged<Type> {
 
 	~data_root()
 	{
+#ifdef FACTOR_DEBUG
+		assert(parent->data_roots.back() == 1);
+#endif
+		parent->data_roots.pop_back();
 #ifdef FACTOR_DEBUG
 		assert(parent->data_roots.back() == (cell)this);
 #endif
diff --git a/vm/gc.cpp b/vm/gc.cpp
index 79f04db802..98266ecc91 100755
--- a/vm/gc.cpp
+++ b/vm/gc.cpp
@@ -218,18 +218,18 @@ void factor_vm::primitive_compact_gc()
 		true /* trace contexts? */);
 }
 
-void factor_vm::inline_gc(cell *data_roots_base, cell data_roots_size)
+void factor_vm::inline_gc(cell data_roots_base, cell data_roots_size)
 {
-	for(cell i = 0; i < data_roots_size; i++)
-		data_roots.push_back((cell)&data_roots_base[i]);
+	data_roots.push_back(data_roots_base);
+	data_roots.push_back(data_roots_size);
 
 	primitive_minor_gc();
 
-	for(cell i = 0; i < data_roots_size; i++)
-		data_roots.pop_back();
+	data_roots.pop_back();
+	data_roots.pop_back();
 }
 
-VM_C_API void inline_gc(cell *data_roots_base, cell data_roots_size, factor_vm *parent)
+VM_C_API void inline_gc(cell data_roots_base, cell data_roots_size, factor_vm *parent)
 {
 	parent->inline_gc(data_roots_base,data_roots_size);
 }
diff --git a/vm/gc.hpp b/vm/gc.hpp
index a9250eddb2..83e5da8aa1 100755
--- a/vm/gc.hpp
+++ b/vm/gc.hpp
@@ -53,6 +53,6 @@ struct gc_state {
 	void start_again(gc_op op_, factor_vm *parent);
 };
 
-VM_C_API void inline_gc(cell *data_roots_base, cell data_roots_size, factor_vm *parent);
+VM_C_API void inline_gc(cell data_roots_base, cell data_roots_size, factor_vm *parent);
 
 }
diff --git a/vm/slot_visitor.hpp b/vm/slot_visitor.hpp
index e777347622..c0263ebf11 100644
--- a/vm/slot_visitor.hpp
+++ b/vm/slot_visitor.hpp
@@ -8,15 +8,18 @@ template<typename Visitor> struct slot_visitor {
 	explicit slot_visitor<Visitor>(factor_vm *parent_, Visitor visitor_) :
 		parent(parent_), visitor(visitor_) {}
 
+	cell visit_pointer(cell pointer)
+	{
+		object *untagged = untag<object>(pointer);
+		untagged = visitor(untagged);
+		return RETAG(untagged,TAG(pointer));
+	}
+
 	void visit_handle(cell *handle)
 	{
 		cell pointer = *handle;
-
-		if(immediate_p(pointer)) return;
-
-		object *untagged = untag<object>(pointer);
-		untagged = visitor(untagged);
-		*handle = RETAG(untagged,TAG(pointer));
+		if(!immediate_p(pointer))
+			*handle = visit_pointer(pointer);
 	}
 
 	void visit_slots(object *ptr, cell payload_start)
@@ -47,8 +50,13 @@ template<typename Visitor> struct slot_visitor {
 		std::vector<cell>::const_iterator iter = parent->data_roots.begin();
 		std::vector<cell>::const_iterator end = parent->data_roots.end();
 
-		for(; iter < end; iter++)
-			visit_handle((cell *)(*iter));
+		while(iter < end)
+		{
+			cell start = *iter++;
+			cell len = *iter++;
+			for(cell index = 0; index < len; index++)
+				visit_handle((cell *)start + index);
+		}
 	}
 
 	void visit_bignum_roots()
diff --git a/vm/vm.hpp b/vm/vm.hpp
index b89dda4085..cb0d0968a0 100755
--- a/vm/vm.hpp
+++ b/vm/vm.hpp
@@ -281,7 +281,7 @@ struct factor_vm
 	void primitive_minor_gc();
 	void primitive_full_gc();
 	void primitive_compact_gc();
-	void inline_gc(cell *data_roots_base, cell data_roots_size);
+	void inline_gc(cell data_roots_base, cell data_roots_size);
 	void primitive_enable_gc_events();
 	void primitive_disable_gc_events();
 	object *allot_object(header header, cell size);