diff --git a/include/openmc/error.h b/include/openmc/error.h
index 062368f17..5f30f0252 100644
--- a/include/openmc/error.h
+++ b/include/openmc/error.h
@@ -7,6 +7,12 @@
 
 #include "openmc/capi.h"
 
+#ifdef __GNUC__
+#define UNREACHABLE() __builtin_unreachable()
+#else
+#define UNREACHABLE() (void)0
+#endif
+
 namespace openmc {
 
 inline void
diff --git a/src/nuclide.cpp b/src/nuclide.cpp
index 7f034fd41..6094b7983 100644
--- a/src/nuclide.cpp
+++ b/src/nuclide.cpp
@@ -454,9 +454,7 @@ double Nuclide::nu(double E, EmissionMode mode, int group) const
       return (*fission_rx_[0]->products_[0].yield_)(E);
     }
   }
-#ifdef __GNUC__
-  __builtin_unreachable();
-#endif
+  UNREACHABLE();
 }
 
 void Nuclide::calculate_elastic_xs(Particle& p) const
diff --git a/src/physics.cpp b/src/physics.cpp
index e28c5a00e..0d0c60343 100644
--- a/src/physics.cpp
+++ b/src/physics.cpp
@@ -883,9 +883,7 @@ Direction sample_target_velocity(const Nuclide* nuc, double E, Direction u,
     } // case RVS, DBRC
   } // switch (sampling_method)
 
-#ifdef __GNUC__
-  __builtin_unreachable();
-#endif
+  UNREACHABLE();
 }
 
 Direction
diff --git a/src/plot.cpp b/src/plot.cpp
index 74279cad5..57466eca1 100644
--- a/src/plot.cpp
+++ b/src/plot.cpp
@@ -693,10 +693,8 @@ void draw_mesh_lines(Plot pl, ImageData& data)
     outer = 1;
     inner = 2;
     break;
-#ifdef __GNUC__
   default:
-    __builtin_unreachable();
-#endif
+    UNREACHABLE();
   }
 
   Position ll_plot {pl.origin_};
diff --git a/src/tallies/filter_particle.cpp b/src/tallies/filter_particle.cpp
index 1d4b84937..23a305b8d 100644
--- a/src/tallies/filter_particle.cpp
+++ b/src/tallies/filter_particle.cpp
@@ -50,9 +50,7 @@ ParticleFilter::text_label(int bin) const
   case Particle::Type::positron:
     return "Particle: positron";
   }
-#ifdef __GNUC__
-  __builtin_unreachable();
-#endif
+  UNREACHABLE();
 }
 
 } // namespace openmc