diff --git a/include/omath/trigonometry/angle.hpp b/include/omath/trigonometry/angle.hpp
index 9d8f9cc..22902b8 100644
--- a/include/omath/trigonometry/angle.hpp
+++ b/include/omath/trigonometry/angle.hpp
@@ -125,7 +125,7 @@ namespace omath
         }
 
         [[nodiscard]]
-        constexpr Angle operator+(const Angle& other) noexcept
+        constexpr Angle operator+(const Angle& other) const noexcept
         {
             if constexpr (flags == AngleFlags::Normalized)
                 return Angle{angles::wrap_angle(m_angle + other.m_angle, min, max)};
@@ -140,7 +140,7 @@ namespace omath
         }
 
         [[nodiscard]]
-        constexpr Angle operator-(const Angle& other) noexcept
+        constexpr Angle operator-(const Angle& other) const noexcept
         {
             return operator+(-other);
         }
diff --git a/tests/general/unit_test_angle.cpp b/tests/general/unit_test_angle.cpp
index 89cc88c..edbe361 100644
--- a/tests/general/unit_test_angle.cpp
+++ b/tests/general/unit_test_angle.cpp
@@ -183,7 +183,7 @@ TEST(UnitTestAngle, Formatter_PrintsDegreesWithSuffix)
 
 TEST(UnitTestAngle, BinaryPlus_ReturnsWrappedSum)
 {
-    Angle<> a = Deg::from_degrees(350.0f);
+    const Angle<> a = Deg::from_degrees(350.0f);
     const Deg b = Deg::from_degrees(20.0f);
     const Deg c = a + b; // expect 10°
     EXPECT_FLOAT_EQ(c.as_degrees(), 10.0f);
@@ -191,7 +191,7 @@ TEST(UnitTestAngle, BinaryPlus_ReturnsWrappedSum)
 
 TEST(UnitTestAngle, BinaryMinus_ReturnsWrappedDiff)
 {
-    Angle<> a = Deg::from_degrees(10.0f);
+    const Angle<> a = Deg::from_degrees(10.0f);
     const Deg b = Deg::from_degrees(30.0f);
     const Deg c = a - b; // expect 340°
     EXPECT_FLOAT_EQ(c.as_degrees(), 340.0f);