diff --git a/src/proc.cpp b/src/proc.cpp
index 24b266920..4d224b8f9 100644
--- a/src/proc.cpp
+++ b/src/proc.cpp
@@ -463,7 +463,7 @@ static bool process_clean_after_marking(bool allow_interactive) {
 
     // This function may fire an event handler, we do not want to call ourselves recursively (to
     // avoid infinite recursion).
-    static bool locked = false;
+    static std::atomic<bool> locked { false };
     if (locked) {
         return false;
     }