diff --git a/persistent-data/data-structures/bitset.cc b/persistent-data/data-structures/bitset.cc
index 9400222..9625dae 100644
--- a/persistent-data/data-structures/bitset.cc
+++ b/persistent-data/data-structures/bitset.cc
@@ -2,6 +2,7 @@
 #include "persistent-data/data-structures/bitset.h"
 #include "persistent-data/math_utils.h"
 
+using namespace boost;
 using namespace persistent_data;
 using namespace persistent_data::bitset_detail;
 using namespace std;
@@ -75,7 +76,52 @@ namespace persistent_data {
 			void flush() {
 			}
 
+			void walk_bitset(bitset_visitor &v) const {
+				bit_visitor vv(v);
+				damage_visitor dv(v);
+				array_.visit_values(vv, dv);
+			}
+
 		private:
+			class bit_visitor {
+			public:
+				bit_visitor(bitset_visitor &v)
+				: v_(v) {
+				}
+
+				void visit(uint32_t word_index, uint64_t word) {
+					uint32_t bit_index = word_index * 64;
+					for (unsigned bit = 0; bit < 64; bit++, bit_index++)
+						v_.visit(bit_index, !!(word & (1 << bit)));
+				}
+
+			private:
+				bitset_visitor &v_;
+			};
+
+			class damage_visitor {
+			public:
+				damage_visitor(bitset_visitor &v)
+					: v_(v) {
+				}
+
+				void visit(array_detail::damage const &d) {
+					run<uint32_t> bits(lifted_mult64(d.lost_keys_.begin_),
+							   lifted_mult64(d.lost_keys_.end_));
+					v_.visit(bits);
+				}
+
+			private:
+				optional<uint32_t> lifted_mult64(optional<uint32_t> const &m) {
+					if (!m)
+						return m;
+
+					return optional<uint32_t>(*m * 64);
+				}
+
+				bitset_visitor &v_;
+			};
+
 			void pad_last_block(bool default_value) {
 				// Set defaults in the final word
 				if (bit(nr_bits_)) {
@@ -198,5 +244,11 @@ bitset::flush()
 	impl_->flush();
 }
 
+void
+bitset::walk_bitset(bitset_visitor &v) const
+{
+	impl_->walk_bitset(v);
+}
+
 //----------------------------------------------------------------
 
diff --git a/persistent-data/data-structures/bitset.h b/persistent-data/data-structures/bitset.h
index 89fa5e1..3e26985 100644
--- a/persistent-data/data-structures/bitset.h
+++ b/persistent-data/data-structures/bitset.h
@@ -19,11 +19,31 @@
 #ifndef BITSET_H
 #define BITSET_H
 
+#include "persistent-data/run.h"
+
 //----------------------------------------------------------------
 
 namespace persistent_data {
 	namespace bitset_detail {
 		class bitset_impl;
+
+		class missing_bits {
+		public:
+			missing_bits(base::run<uint32_t> const &keys)
+				: keys_(keys) {
+			}
+
+			base::run<uint32_t> keys_;
+		};
+
+		class bitset_visitor {
+		public:
+			typedef boost::shared_ptr<bitset_visitor> ptr;
+
+			virtual ~bitset_visitor();
+			virtual void visit(uint32_t index, bool value);
+			virtual void visit(missing_bits const &d);
+		};
 	}
 
 	class bitset {
@@ -42,6 +62,8 @@ namespace persistent_data {
 		void set(unsigned n, bool value);
 		void flush();
 
+		void walk_bitset(bitset_detail::bitset_visitor &v) const;
+
 	private:
 		boost::shared_ptr<bitset_detail::bitset_impl> impl_;
 	};