--- a/core/src/luan/impl/UnmExpr.java	Mon Jul 13 20:53:02 2015 -0600
+++ b/core/src/luan/impl/UnmExpr.java	Tue Jul 14 17:40:48 2015 -0600
@@ -26,7 +26,7 @@
 					return Luan.first(fn.call(luan,new Object[]{o}));
 				}
 			}
-			throw luan.exception("attempt to perform arithmetic on a "+Luan.type(o)+" value");
+			throw new LuanException(luan,"attempt to perform arithmetic on a "+Luan.type(o)+" value");
 		} finally {
 			luan.pop();
 		}