diff --git a/prada2012/ch02/print_roots2.adb b/prada2012/ch02/print_roots2.adb
index e47ed1c..12807df 100644
--- a/prada2012/ch02/print_roots2.adb
+++ b/prada2012/ch02/print_roots2.adb
@@ -1,11 +1,13 @@
 -- print_roots2 demonstrates runtime exceptions.
 with Ada.Text_IO;
 with Ada.Float_Text_IO;
+with Ada.Numerics;
 with Ada.Numerics.Generic_Elementary_Functions;
 
-procedure Print_Roots is
+procedure Print_Roots2 is
 	use Ada.Text_IO;
 	use Ada.Float_Text_IO;
+	use Ada.Numerics;
 	package Numerics is new Ada.Numerics.Generic_Elementary_Functions(Float);
 	use Numerics;
 	X: Float;
@@ -16,8 +18,15 @@ begin
 	loop
 		Get(X);
 		exit when X = 0.0;
-		Put("Root of "); Put(X); Put(" is ");
+		begin
+			Put("Root of "); Put(X); Put(" is ");
+		exception
+			when Ada.Numerics.Argument_Error =>
+				Put("not calculable: X must be >= 0");
+			when Constraint_Error =>
+				Put("not calculable: X must be >= 0");
+		end;
 		Put(Sqrt(X));
 		New_Line;
 	end loop;
-end Print_Roots;
+end Print_Roots2;