diff --git a/include/pocketpy/common/threads.h b/include/pocketpy/common/threads.h
index adf5d047..0791433a 100644
--- a/include/pocketpy/common/threads.h
+++ b/include/pocketpy/common/threads.h
@@ -1,3 +1,5 @@
+#pragma once
+
 #include <stdatomic.h>
 #include <stdbool.h>