diff --git a/src/utf8.hh b/src/utf8.hh
index 116c225e..20199030 100644
--- a/src/utf8.hh
+++ b/src/utf8.hh
@@ -107,7 +107,7 @@ struct Pass
 
 // returns the codepoint of the character whose first byte
 // is pointed by it
-template<typename InvalidPolicy = utf8::InvalidPolicy::Assert,
+template<typename InvalidPolicy = utf8::InvalidPolicy::Pass,
          typename Iterator>
 Codepoint codepoint(Iterator it, Iterator end)
 {
@@ -146,7 +146,7 @@ Codepoint codepoint(Iterator it, Iterator end)
     return InvalidPolicy{}(byte);
 }
 
-template<typename InvalidPolicy = utf8::InvalidPolicy::Assert>
+template<typename InvalidPolicy = utf8::InvalidPolicy::Pass>
 ByteCount codepoint_size(char byte)
 {
     if (not (byte & 0x80)) // 0xxxxxxx
@@ -160,7 +160,7 @@ ByteCount codepoint_size(char byte)
     else
     {
         InvalidPolicy{}(byte);
-        return -1;
+        return 1;
     }
 }
 
diff --git a/src/utf8_iterator.hh b/src/utf8_iterator.hh
index d2d8fa6a..1637fe2d 100644
--- a/src/utf8_iterator.hh
+++ b/src/utf8_iterator.hh
@@ -12,7 +12,7 @@ namespace utf8
 // adapter for an iterator on bytes which permits to iterate
 // on unicode codepoints instead.
 template<typename Iterator,
-         typename InvalidPolicy = utf8::InvalidPolicy::Assert>
+         typename InvalidPolicy = utf8::InvalidPolicy::Pass>
 class iterator
 {
 public:
@@ -140,7 +140,7 @@ private:
     mutable Codepoint m_value = -1;
 };
 
-template<typename InvalidPolicy = utf8::InvalidPolicy::Assert, typename Iterator>
+template<typename InvalidPolicy = utf8::InvalidPolicy::Pass, typename Iterator>
 iterator<Iterator, InvalidPolicy> make_iterator(Iterator it)
 {
     return iterator<Iterator, InvalidPolicy>{std::move(it)};