diff --git a/src/core/include/mp-units/framework/unit_magnitude.h b/src/core/include/mp-units/framework/unit_magnitude.h
index 0659c7c5..81b512c6 100644
--- a/src/core/include/mp-units/framework/unit_magnitude.h
+++ b/src/core/include/mp-units/framework/unit_magnitude.h
@@ -42,7 +42,7 @@ namespace mp_units {
 
 MP_UNITS_EXPORT_BEGIN
 
-#if defined MP_UNITS_COMP_CLANG || MP_UNITS_COMP_CLANG < 18
+#if defined MP_UNITS_COMP_CLANG && MP_UNITS_COMP_CLANG < 18
 
 template<symbol_text Symbol>
 struct mag_constant {
@@ -86,7 +86,7 @@ constexpr UnitMagnitude auto mag_power = pow<Num, Den>(mag<Base>);
 /**
  * @brief  A convenient Magnitude constant for pi, which we can manipulate like a regular number.
  */
-#if defined MP_UNITS_COMP_CLANG || MP_UNITS_COMP_CLANG < 18
+#if defined MP_UNITS_COMP_CLANG && MP_UNITS_COMP_CLANG < 18
 inline constexpr struct pi final : mag_constant<symbol_text{u8"π" /* U+03C0 GREEK SMALL LETTER PI */, "pi"}> {
   static constexpr auto _value_ = std::numbers::pi_v<long double>;
 #else
diff --git a/src/core/include/mp-units/framework/unit_magnitude_concepts.h b/src/core/include/mp-units/framework/unit_magnitude_concepts.h
index be055212..2586cfef 100644
--- a/src/core/include/mp-units/framework/unit_magnitude_concepts.h
+++ b/src/core/include/mp-units/framework/unit_magnitude_concepts.h
@@ -38,7 +38,7 @@ import std;
 
 namespace mp_units {
 
-#if defined MP_UNITS_COMP_CLANG || MP_UNITS_COMP_CLANG < 18
+#if defined MP_UNITS_COMP_CLANG && MP_UNITS_COMP_CLANG < 18
 MP_UNITS_EXPORT template<symbol_text Symbol>
 #else
 MP_UNITS_EXPORT template<symbol_text Symbol, long double Value>
diff --git a/test/static/unit_symbol_test.cpp b/test/static/unit_symbol_test.cpp
index 4a1d01dd..03e44477 100644
--- a/test/static/unit_symbol_test.cpp
+++ b/test/static/unit_symbol_test.cpp
@@ -142,7 +142,7 @@ static_assert(unit_symbol<usf{.char_set = portable}>(mag_ratio<1, 18000> * (metr
 // static_assert(unit_symbol<usf{.char_set = portable}>(mag<1> / mag_power<2, 1, 2> * m) == "(1/2^(1/2) m)");
 
 // magnitude constants
-#if defined MP_UNITS_COMP_CLANG || MP_UNITS_COMP_CLANG < 18
+#if defined MP_UNITS_COMP_CLANG && MP_UNITS_COMP_CLANG < 18
 inline constexpr struct e final : mag_constant<"e"> {
   static constexpr long double _value_ = std::numbers::e_v<long double>;
 #else