diff --git a/examples/roman3.py b/examples/roman3.py
index 561018e..b03e1d6 100644
--- a/examples/roman3.py
+++ b/examples/roman3.py
@@ -23,7 +23,7 @@ roman_numeral_map = (('M',  1000),
 def to_roman(n):
     '''convert integer to Roman numeral'''
     if not (0 < n < 4000):
-        raise OutOfRangeError('number out of range (must be 0..3999)')
+        raise OutOfRangeError('number out of range (must be 1..3999)')
 
     result = ''
     for numeral, integer in roman_numeral_map:
diff --git a/examples/roman4.py b/examples/roman4.py
index cfd6de7..3315cc3 100644
--- a/examples/roman4.py
+++ b/examples/roman4.py
@@ -24,7 +24,7 @@ roman_numeral_map = (('M',  1000),
 def to_roman(n):
     '''convert integer to Roman numeral'''
     if not (0 < n < 4000):
-        raise OutOfRangeError('number out of range (must be 0..3999)')
+        raise OutOfRangeError('number out of range (must be 1..3999)')
     if not isinstance(n, int):
         raise NotIntegerError('non-integers can not be converted')
 
diff --git a/examples/roman5.py b/examples/roman5.py
index a230672..41a870f 100644
--- a/examples/roman5.py
+++ b/examples/roman5.py
@@ -24,7 +24,7 @@ roman_numeral_map = (('M',  1000),
 def to_roman(n):
     '''convert integer to Roman numeral'''
     if not (0 < n < 4000):
-        raise OutOfRangeError('number out of range (must be 0..3999)')
+        raise OutOfRangeError('number out of range (must be 1..3999)')
     if not isinstance(n, int):
         raise NotIntegerError('non-integers can not be converted')
 
diff --git a/examples/roman6.py b/examples/roman6.py
index 512e7ff..39cc52b 100644
--- a/examples/roman6.py
+++ b/examples/roman6.py
@@ -39,7 +39,7 @@ roman_numeral_pattern = re.compile('''
 def to_roman(n):
     '''convert integer to Roman numeral'''
     if not (0 < n < 4000):
-        raise OutOfRangeError('number out of range (must be 0..3999)')
+        raise OutOfRangeError('number out of range (must be 1..3999)')
     if not isinstance(n, int):
         raise NotIntegerError('non-integers can not be converted')
 
diff --git a/examples/roman7.py b/examples/roman7.py
index 2346d09..616158d 100644
--- a/examples/roman7.py
+++ b/examples/roman7.py
@@ -39,7 +39,7 @@ roman_numeral_pattern = re.compile('''
 def to_roman(n):
     '''convert integer to Roman numeral'''
     if not (0 < n < 4000):
-        raise OutOfRangeError('number out of range (must be 0..3999)')
+        raise OutOfRangeError('number out of range (must be 1..3999)')
     if not isinstance(n, int):
         raise NotIntegerError('non-integers can not be converted')
 
diff --git a/examples/roman8.py b/examples/roman8.py
index 2fbd825..1069dc5 100644
--- a/examples/roman8.py
+++ b/examples/roman8.py
@@ -39,7 +39,7 @@ roman_numeral_pattern = re.compile('''
 def to_roman(n):
     '''convert integer to Roman numeral'''
     if not (0 < n < 4000):
-        raise OutOfRangeError('number out of range (must be 0..3999)')
+        raise OutOfRangeError('number out of range (must be 1..3999)')
     if not isinstance(n, int):
         raise NotIntegerError('non-integers can not be converted')
 
diff --git a/unit-testing.html b/unit-testing.html
index 3109530..1c679b5 100755
--- a/unit-testing.html
+++ b/unit-testing.html
@@ -420,7 +420,7 @@ FAILED (failures=2)</samp></pre>
 <pre class=pp><code>def to_roman(n):
     '''convert integer to Roman numeral'''
 <a>    if not (0 &lt; n &lt; 4000):                                              <span class=u>&#x2460;</span></a>
-<a>        raise OutOfRangeError('number out of range (must be 0..3999)')  <span class=u>&#x2461;</span></a>
+<a>        raise OutOfRangeError('number out of range (must be 1..3999)')  <span class=u>&#x2461;</span></a>
 
     result = ''
     for numeral, integer in roman_numeral_map:
@@ -517,7 +517,7 @@ FAILED (failures=1)</samp></pre>
 <pre class=pp><code>def to_roman(n):
     '''convert integer to Roman numeral'''
     if not (0 &lt; n &lt; 4000):
-        raise OutOfRangeError('number out of range (must be 0..3999)')
+        raise OutOfRangeError('number out of range (must be 1..3999)')
 <a>    if not isinstance(n, int):                                          <span class=u>&#x2460;</span></a>
 <a>        raise NotIntegerError('non-integers can not be converted')      <span class=u>&#x2461;</span></a>