diff --git a/au/code/au/units/pascals.hh b/au/code/au/units/pascals.hh
index bc86df89..a2a81560 100644
--- a/au/code/au/units/pascals.hh
+++ b/au/code/au/units/pascals.hh
@@ -33,7 +33,13 @@ constexpr const char PascalsLabel<T>::label[];
 struct Pascals : decltype(Newtons{} / squared(Meters{})), PascalsLabel<void> {
     using PascalsLabel<void>::label;
 };
-constexpr auto pascal = SingularNameFor<Pascals>{};
+
+#ifndef pascal
+[[deprecated(
+    "Conflicts with the `pascal` macro from <Windows.h>; declare manually "
+    "instead.")]] constexpr auto pascal = SingularNameFor<Pascals>{};
+#endif
+
 constexpr auto pascals = QuantityMaker<Pascals>{};
 constexpr QuantityPointMaker<Pascals> pascals_pt{};