diff --git a/include/c11log/details/null_mutex.h b/include/c11log/details/null_mutex.h
new file mode 100644
index 00000000..5a87cd02
--- /dev/null
+++ b/include/c11log/details/null_mutex.h
@@ -0,0 +1,17 @@
+#pragma once
+
+// null, no cost mutex
+
+namespace c11log {
+namespace details {
+struct null_mutex
+{
+    void lock() {}
+    void unlock() {}
+    bool try_lock()
+    {
+        return true;
+    }
+};
+}
+}