diff --git a/src/core/include/units/bits/basic_concepts.h b/src/core/include/units/bits/basic_concepts.h
index 974bccd4..e31e922e 100644
--- a/src/core/include/units/bits/basic_concepts.h
+++ b/src/core/include/units/bits/basic_concepts.h
@@ -28,7 +28,6 @@
 #include <units/customization_points.h>
 #include <units/ratio.h>
 #include <units/bits/external/type_traits.h>
-#include <functional>
 #include <cstdint>
 #include <utility>