diff --git a/include/openmc/surface.h b/include/openmc/surface.h
index 9cdc460bb..d61ae07ce 100644
--- a/include/openmc/surface.h
+++ b/include/openmc/surface.h
@@ -83,13 +83,6 @@ struct BoundingBox
     return *this;
   }
 
-  inline bool is_valid() {
-    return xmin <= xmax &&
-           ymin <= ymax &&
-           zmin <= zmax;
-  }
-
-
 };
 
 //==============================================================================