diff --git a/src/fmt.cc b/src/fmt.cc
index f319ce94..6d1d73b5 100644
--- a/src/fmt.cc
+++ b/src/fmt.cc
@@ -19,6 +19,7 @@ module;
 // to prevent attachment to this module.
 #ifndef FMT_IMPORT_STD
 #  include <algorithm>
+#  include <atomic>
 #  include <bitset>
 #  include <chrono>
 #  include <cmath>