diff --git a/include/interactive_markers/message_context.hpp b/include/interactive_markers/message_context.hpp
index 0ecd48eb..fbefbbc8 100644
--- a/include/interactive_markers/message_context.hpp
+++ b/include/interactive_markers/message_context.hpp
@@ -60,7 +60,7 @@ class MessageContext
 
   MessageContext(const MessageContext &) = default;
 
-  MessageContext<MsgT> & operator=(const MessageContext<MsgT> & other);
+  MessageContext<MsgT> & operator=(const MessageContext<MsgT> & other) = default;
 
   // transform all messages with timestamp into target frame
   void getTfTransforms();
diff --git a/src/interactive_marker_server.cpp b/src/interactive_marker_server.cpp
index 205a44d9..f14725f7 100644
--- a/src/interactive_marker_server.cpp
+++ b/src/interactive_marker_server.cpp
@@ -377,6 +377,8 @@ void InteractiveMarkerServer::getInteractiveMarkersCallback(
   (void)request_header;
   (void)request;
 
+  std::unique_lock<std::recursive_mutex> lock(mutex_);
+
   RCLCPP_DEBUG(logger_, "Responding to request to get interactive markers");
   response->sequence_number = sequence_number_;
   response->markers.reserve(marker_contexts_.size());
diff --git a/src/message_context.cpp b/src/message_context.cpp
index c2270ae0..75b21371 100644
--- a/src/message_context.cpp
+++ b/src/message_context.cpp
@@ -75,16 +75,6 @@ MessageContext<MsgT>::MessageContext(
   init();
 }
 
-template<class MsgT>
-MessageContext<MsgT> & MessageContext<MsgT>::operator=(const MessageContext<MsgT> & other)
-{
-  open_marker_idx_ = other.open_marker_idx_;
-  open_pose_idx_ = other.open_pose_idx_;
-  target_frame_ = other.target_frame_;
-  enable_autocomplete_transparency_ = other.enable_autocomplete_transparency_;
-  return *this;
-}
-
 template<class MsgT>
 bool MessageContext<MsgT>::getTransform(
   std_msgs::msg::Header & header,
diff --git a/src/tools.cpp b/src/tools.cpp
index b30ec8ab..4608ac7d 100644
--- a/src/tools.cpp
+++ b/src/tools.cpp
@@ -34,6 +34,7 @@
 #endif
 
 #include <algorithm>
+#include <atomic>
 #include <cmath>
 #include <format>  // NOLINT(build/include_order): cpplint misclassifies the C++20 header as C
 #include <set>
@@ -189,8 +190,8 @@ void autoComplete(
     marker.pose.orientation.z = marker_orientation.z();
     marker.pose.orientation.w = marker_orientation.w();
 
-    static unsigned id = 0;
-    marker.id = id++;
+    static std::atomic<unsigned> id{0};
+    marker.id = id.fetch_add(1, std::memory_order_relaxed);
     marker.ns = msg.name;
 
     // If transparency is disabled, set alpha to 1.0 for all semi-transparent markers