diff --git a/parallel_hashmap/phmap.h b/parallel_hashmap/phmap.h
index 2a5ff42..82b47bd 100644
--- a/parallel_hashmap/phmap.h
+++ b/parallel_hashmap/phmap.h
@@ -45,6 +45,7 @@
 #include <utility>
 #include <array>
 #include <cassert>
+#include <atomic>
 
 #include "phmap_utils.h"
 #include "phmap_base.h"