diff --git a/src/core/include/mp-units/dimension.h b/src/core/include/mp-units/dimension.h
index 6ab680f4..0ddd22bf 100644
--- a/src/core/include/mp-units/dimension.h
+++ b/src/core/include/mp-units/dimension.h
@@ -24,6 +24,7 @@
 
 #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/external/type_traits.h>
 #include <mp-units/bits/module_macros.h>
 #include <mp-units/bits/symbol_text.h>
@@ -305,7 +306,11 @@ template<typename CharT, std::size_t N, dimension_symbol_formatting fmt, Dimensi
 // TODO Refactor to `dimension_symbol(D, fmt)` when P1045: constexpr Function Parameters is available
 MP_UNITS_EXPORT template<dimension_symbol_formatting fmt = dimension_symbol_formatting{}, typename CharT = char,
                          Dimension D>
+#if defined MP_UNITS_COMP_CLANG && MP_UNITS_COMP_CLANG <= 18
+[[nodiscard]] constexpr auto dimension_symbol(D)
+#else
 [[nodiscard]] consteval auto dimension_symbol(D)
+#endif
 {
   auto get_size = []() consteval {
     std::basic_string<CharT> buffer;
diff --git a/src/core/include/mp-units/unit.h b/src/core/include/mp-units/unit.h
index ca63e0b2..4526333e 100644
--- a/src/core/include/mp-units/unit.h
+++ b/src/core/include/mp-units/unit.h
@@ -25,6 +25,7 @@
 #include <mp-units/bits/expression_template.h>
 #include <mp-units/bits/external/algorithm.h>
 #include <mp-units/bits/external/fixed_string.h>
+#include <mp-units/bits/external/hacks.h>
 #include <mp-units/bits/external/type_name.h>
 #include <mp-units/bits/external/type_traits.h>
 #include <mp-units/bits/get_associated_quantity.h>
@@ -826,7 +827,11 @@ template<typename CharT, std::size_t N, unit_symbol_formatting fmt, Unit U>
 
 // TODO Refactor to `unit_symbol(U, fmt)` when P1045: constexpr Function Parameters is available
 MP_UNITS_EXPORT template<unit_symbol_formatting fmt = unit_symbol_formatting{}, typename CharT = char, Unit U>
+#if defined MP_UNITS_COMP_CLANG && MP_UNITS_COMP_CLANG <= 18
+[[nodiscard]] constexpr auto unit_symbol(U)
+#else
 [[nodiscard]] consteval auto unit_symbol(U)
+#endif
 {
   auto get_size = []() consteval {
     std::basic_string<CharT> buffer;