diff --git a/src/benchmark.cc b/src/benchmark.cc
index b7767bd00..1aa432b8b 100644
--- a/src/benchmark.cc
+++ b/src/benchmark.cc
@@ -663,6 +663,10 @@ void RegisterMemoryManager(MemoryManager* manager) {
 }
 
 void RegisterProfilerManager(ProfilerManager* manager) {
+  // Don't allow overwriting an existing manager.
+  if (manager != nullptr) {
+    BM_CHECK_EQ(internal::profiler_manager, nullptr);
+  }
   internal::profiler_manager = manager;
 }