diff --git a/parallel_hashmap/phmap.h b/parallel_hashmap/phmap.h
index 653ae5e..cc37297 100644
--- a/parallel_hashmap/phmap.h
+++ b/parallel_hashmap/phmap.h
@@ -3094,6 +3094,29 @@ public:
         return std::get<2>(res);
     }
 
+    // Extension API: support iterating over all values
+    //
+    // flat_hash_set<std::string> s;
+    // s.insert(...);
+    // s.for_each([](auto const & key) {
+    //    // Safely iterates over all the keys
+    // });
+    template <class F>
+    void for_each(F&& fCallback) const {
+        for (auto const& inner : sets_) {
+            typename Lockable::SharedLock m(const_cast<Inner&>(inner));
+            std::for_each(inner.set_.begin(), inner.set_.end(), fCallback);
+        }
+    }
+
+    // this version allows to modify the values
+    void for_each_m(std::function<void (value_type&)> && fCallback) {
+        for (auto& inner : sets_) {
+            typename Lockable::UniqueLock m(const_cast<Inner&>(inner));
+            std::for_each(inner.set_.begin(), inner.set_.end(), fCallback);
+        }
+    }
+
     // Extension API: support for heterogeneous keys.
     //
     //   std::unordered_set<std::string> s;
diff --git a/tests/parallel_hash_map_test.cc b/tests/parallel_hash_map_test.cc
index 4e060db..a740d4d 100644
--- a/tests/parallel_hash_map_test.cc
+++ b/tests/parallel_hash_map_test.cc
@@ -100,6 +100,22 @@ TEST(THIS_TEST_NAME, ThreadSafeContains) {
         EXPECT_EQ(m[5], 0);
     }
 
+    {
+        // -------------
+        // test for_each
+        // -------------
+        Map m = { {1, 7}, {2, 8}, {5, 11} };
+
+        // increment all values by 1
+        m.for_each_m([](auto &pair) {  ++pair.second; });
+
+        int counter = 0;
+        m.for_each([&counter](auto const &pair) {
+            ++counter;
+            EXPECT_EQ(pair.first + 7, pair.second);
+        });
+        EXPECT_EQ(counter, 3);
+    }
 }
 
 }  // namespace