diff --git a/rclcpp/include/rclcpp/intra_process_manager_impl.hpp b/rclcpp/include/rclcpp/intra_process_manager_impl.hpp
index 8c4754c..89c6f0c 100644
--- a/rclcpp/include/rclcpp/intra_process_manager_impl.hpp
+++ b/rclcpp/include/rclcpp/intra_process_manager_impl.hpp
@@ -139,13 +139,14 @@ public:
     uint64_t intra_process_publisher_id,
     uint64_t & message_seq)
   {
+    std::lock_guard<std::mutex> lock(runtime_mutex_);
     auto it = publishers_.find(intra_process_publisher_id);
     if (it == publishers_.end()) {
       throw std::runtime_error("store_intra_process_message called with invalid publisher id");
     }
     PublisherInfo & info = it->second;
     // Calculate the next message sequence number.
-    message_seq = info.sequence_number.fetch_add(1, std::memory_order_relaxed);
+    message_seq = info.sequence_number.fetch_add(1);
 
     return info.buffer;
   }
diff --git a/rclcpp/include/rclcpp/mapped_ring_buffer.hpp b/rclcpp/include/rclcpp/mapped_ring_buffer.hpp
index ce66ceb..d9fb736 100644
--- a/rclcpp/include/rclcpp/mapped_ring_buffer.hpp
+++ b/rclcpp/include/rclcpp/mapped_ring_buffer.hpp
@@ -19,6 +19,7 @@
 #include <cstddef>
 #include <cstdint>
 #include <memory>
+#include <mutex>
 #include <vector>
 
 #include "rclcpp/allocator/allocator_common.hpp"
@@ -97,6 +98,7 @@ public:
   void
   get_copy_at_key(uint64_t key, ElemUniquePtr & value)
   {
+    std::lock_guard<std::mutex> lock(data_mutex_);
     auto it = get_iterator_of_key(key);
     value = nullptr;
     if (it != elements_.end() && it->in_use) {
@@ -128,6 +130,7 @@ public:
   void
   get_ownership_at_key(uint64_t key, ElemUniquePtr & value)
   {
+    std::lock_guard<std::mutex> lock(data_mutex_);
     auto it = get_iterator_of_key(key);
     value = nullptr;
     if (it != elements_.end() && it->in_use) {
@@ -155,6 +158,7 @@ public:
   void
   pop_at_key(uint64_t key, ElemUniquePtr & value)
   {
+    std::lock_guard<std::mutex> lock(data_mutex_);
     auto it = get_iterator_of_key(key);
     value = nullptr;
     if (it != elements_.end() && it->in_use) {
@@ -177,6 +181,7 @@ public:
   bool
   push_and_replace(uint64_t key, ElemUniquePtr & value)
   {
+    std::lock_guard<std::mutex> lock(data_mutex_);
     bool did_replace = elements_[head_].in_use;
     elements_[head_].key = key;
     elements_[head_].value.swap(value);
@@ -196,6 +201,7 @@ public:
   bool
   has_key(uint64_t key)
   {
+    std::lock_guard<std::mutex> lock(data_mutex_);
     return elements_.end() != get_iterator_of_key(key);
   }
 
@@ -225,6 +231,7 @@ private:
   std::vector<element, VectorAlloc> elements_;
   size_t head_;
   std::shared_ptr<ElemAlloc> allocator_;
+  std::mutex data_mutex_;
 };
 
 }  // namespace mapped_ring_buffer
diff --git a/rclcpp/include/rclcpp/publisher.hpp b/rclcpp/include/rclcpp/publisher.hpp
index 2268212..7ec46e8 100644
--- a/rclcpp/include/rclcpp/publisher.hpp
+++ b/rclcpp/include/rclcpp/publisher.hpp
@@ -18,9 +18,9 @@
 #include <rmw/error_handling.h>
 #include <rmw/rmw.h>
 
+#include <functional>
 #include <iostream>
 #include <memory>
-#include <mutex>
 #include <sstream>
 #include <string>