diff --git a/src/supervisor/Supervisor.cc b/src/supervisor/Supervisor.cc
index 48894d1f0e..974367c87c 100644
--- a/src/supervisor/Supervisor.cc
+++ b/src/supervisor/Supervisor.cc
@@ -415,7 +415,7 @@ static ForkResult fork_with_stdio_redirect(const char* where) {
 
 void Supervisor::HandleChildSignal() {
     if ( last_signal >= 0 ) {
-        DBG_LOG(DBG_SUPERVISOR, "Supervisor received signal %d", last_signal);
+        DBG_LOG(DBG_SUPERVISOR, "Supervisor received signal %d", last_signal.load());
         last_signal = -1;
     }
 
diff --git a/src/supervisor/Supervisor.h b/src/supervisor/Supervisor.h
index c433c0536a..84c5595138 100644
--- a/src/supervisor/Supervisor.h
+++ b/src/supervisor/Supervisor.h
@@ -3,6 +3,7 @@
 #pragma once
 
 #include <sys/types.h>
+#include <atomic>
 #include <chrono>
 #include <map>
 #include <memory>
@@ -323,7 +324,7 @@ private:
 
     Config config;
     pid_t stem_pid;
-    int last_signal = -1;
+    std::atomic<int> last_signal = -1;
     std::unique_ptr<detail::PipePair> stem_pipe;
     detail::LineBufferedPipe stem_stdout;
     detail::LineBufferedPipe stem_stderr;