diff --git a/pull/include/prometheus/exposer.h b/pull/include/prometheus/exposer.h
index b470fbd0..83e0e7f0 100644
--- a/pull/include/prometheus/exposer.h
+++ b/pull/include/prometheus/exposer.h
@@ -3,6 +3,7 @@
 #include <cstddef>
 #include <functional>
 #include <memory>
+#include <mutex>
 #include <string>
 #include <vector>
 
@@ -50,6 +51,7 @@ class PROMETHEUS_CPP_PULL_EXPORT Exposer {
 
   std::unique_ptr<CivetServer> server_;
   std::vector<std::unique_ptr<detail::Endpoint>> endpoints_;
+  std::mutex mutex_;
 };
 
 }  // namespace prometheus
diff --git a/pull/src/exposer.cc b/pull/src/exposer.cc
index 546c9bc1..5ee3adea 100644
--- a/pull/src/exposer.cc
+++ b/pull/src/exposer.cc
@@ -27,6 +27,7 @@ Exposer::~Exposer() = default;
 
 void Exposer::RegisterCollectable(const std::weak_ptr<Collectable>& collectable,
                                   const std::string& uri) {
+  std::lock_guard<std::mutex> lock{mutex_};
   auto& endpoint = GetEndpointForUri(uri);
   endpoint.RegisterCollectable(collectable);
 }
@@ -34,12 +35,14 @@ void Exposer::RegisterCollectable(const std::weak_ptr<Collectable>& collectable,
 void Exposer::RegisterAuth(
     std::function<bool(const std::string&, const std::string&)> authCB,
     const std::string& realm, const std::string& uri) {
+  std::lock_guard<std::mutex> lock{mutex_};
   auto& endpoint = GetEndpointForUri(uri);
   endpoint.RegisterAuth(std::move(authCB), realm);
 }
 
 void Exposer::RemoveCollectable(const std::weak_ptr<Collectable>& collectable,
                                 const std::string& uri) {
+  std::lock_guard<std::mutex> lock{mutex_};
   auto& endpoint = GetEndpointForUri(uri);
   endpoint.RemoveCollectable(collectable);
 }