gcc8: error: expression '<throw-expression>' is not a constant expression

Index: al/effects/chorus.cpp
--- al/effects/chorus.cpp.orig
+++ al/effects/chorus.cpp
@@ -42,9 +42,10 @@ constexpr ALenum EnumFromWaveform(ChorusWaveform type)
     {
     case ChorusWaveform::Sinusoid: return AL_CHORUS_WAVEFORM_SINUSOID;
     case ChorusWaveform::Triangle: return AL_CHORUS_WAVEFORM_TRIANGLE;
+    default:
+        throw std::runtime_error{fmt::format("Invalid chorus waveform: {}",
+            int{al::to_underlying(type)})};
     }
-    throw std::runtime_error{fmt::format("Invalid chorus waveform: {}",
-        int{al::to_underlying(type)})};
 }
 
 constexpr EffectProps genDefaultChorusProps() noexcept
