diff --git a/src/core/include/mp-units/bits/quantity_spec_concepts.h b/src/core/include/mp-units/bits/quantity_spec_concepts.h
index c45b345c..d04e8bd7 100644
--- a/src/core/include/mp-units/bits/quantity_spec_concepts.h
+++ b/src/core/include/mp-units/bits/quantity_spec_concepts.h
@@ -22,9 +22,9 @@
 
 #pragma once
 
-#include <mp-units/bits/external/hacks.h>
 #include <mp-units/bits/dimension_concepts.h>
 #include <mp-units/bits/expression_template.h>
+#include <mp-units/bits/external/hacks.h>
 #include <mp-units/bits/module_macros.h>
 
 namespace mp_units {