diff --git a/examples/roman9.py b/examples/roman9.py
index 64134b5..e97f75a 100644
--- a/examples/roman9.py
+++ b/examples/roman9.py
@@ -39,7 +39,7 @@ roman_numeral_pattern = re.compile('''
 def to_roman(n):
     '''convert integer to Roman numeral'''
     if not (0 < n < 5000):
-        raise OutOfRangeError('number out of range (must be 0..4999)')
+        raise OutOfRangeError('number out of range (must be 1..4999)')
     if not isinstance(n, int):
         raise NotIntegerError('non-integers can not be converted')
 
diff --git a/refactoring.html b/refactoring.html
index 06c87cc..7be2929 100755
--- a/refactoring.html
+++ b/refactoring.html
@@ -241,7 +241,7 @@ FAILED (errors=3)</samp></pre>
 def to_roman(n):
     '''convert integer to Roman numeral'''
 <a>    if not (0 &lt; n &lt; 5000):                        <span class=u>&#x2461;</span></a>
-        raise OutOfRangeError('number out of range (must be 0..4999)')
+        raise OutOfRangeError('number out of range (must be 1..4999)')
     if not isinstance(n, int):
         raise NotIntegerError('non-integers can not be converted')