diff --git a/include/tidyenum.h b/include/tidyenum.h
index 313b1a3..f7cb3c7 100644
--- a/include/tidyenum.h
+++ b/include/tidyenum.h
@@ -171,6 +171,7 @@ extern "C" {
     FN(ESCAPED_ILLEGAL_URI)           \
     FN(FIXED_BACKSLASH)               \
     FN(ID_NAME_MISMATCH)              \
+    FN(ILLEGAL_URI_CODEPOINT)         \
     FN(ILLEGAL_URI_REFERENCE)         \
     FN(INSERTING_AUTO_ATTRIBUTE)      \
     FN(INVALID_ATTRIBUTE)             \
diff --git a/src/attrs.c b/src/attrs.c
index 467a814..cbcb6a9 100644
--- a/src/attrs.c
+++ b/src/attrs.c
@@ -1476,15 +1476,64 @@ static void CheckLowerCaseAttrValue( TidyDocImpl* doc, Node *node, AttVal *attva
 
 /* methods for checking value of a specific attribute */
 
+static Bool IsURLCodePoint( ctmbstr p, uint *increment )
+{
+    uint c;
+    *increment = TY_(GetUTF8)( p, &c ) + 1;
+
+    return isalnum( c ) ||
+        c == '%' ||    /* not a valid codepoint, but an escape sequence */
+        c == '#' ||    /* not a valid codepoint, but a delimiter */
+        c == '!' ||
+        c == '$' ||
+        c == '&' ||
+        c == '\'' ||
+        c == '(' ||
+        c == ')' ||
+        c == '*' ||
+        c == '+' ||
+        c == ',' ||
+        c == '-' ||
+        c == '.' ||
+        c == '/' ||
+        c == ':' ||
+        c == ';' ||
+        c == '=' ||
+        c == '?' ||
+        c == '@' ||
+        c == '_' ||
+        c == '~' ||
+        (c >= 0x00A0 && c <= 0xD7FF) ||
+        (c >= 0xE000 && c <= 0xFDCF) ||
+        (c >= 0xFDF0 && c <= 0xFFEF) ||
+        (c >= 0x10000 && c <= 0x1FFFD) ||
+        (c >= 0x20000 && c <= 0x2FFFD) ||
+        (c >= 0x30000 && c <= 0x3FFFD) ||
+        (c >= 0x40000 && c <= 0x4FFFD) ||
+        (c >= 0x50000 && c <= 0x5FFFD) ||
+        (c >= 0x60000 && c <= 0x6FFFD) ||
+        (c >= 0x70000 && c <= 0x7FFFD) ||
+        (c >= 0x80000 && c <= 0x8FFFD) ||
+        (c >= 0x90000 && c <= 0x9FFFD) ||
+        (c >= 0xA0000 && c <= 0xAFFFD) ||
+        (c >= 0xB0000 && c <= 0xBFFFD) ||
+        (c >= 0xC0000 && c <= 0xCFFFD) ||
+        (c >= 0xD0000 && c <= 0xDFFFD) ||
+        (c >= 0xE0000 && c <= 0xEFFFD) ||
+        (c >= 0xF0000 && c <= 0xFFFFD) ||
+        (c >= 0x100000 && c <= 0x10FFFD);
+}
+
 void TY_(CheckUrl)( TidyDocImpl* doc, Node *node, AttVal *attval)
 {
-    tmbchar c; 
+    tmbchar c;
     tmbstr dest, p;
-    uint escape_count = 0, backslash_count = 0;
+    uint escape_count = 0, backslash_count = 0, bad_codepoint_count = 0;
     uint i, pos = 0;
     uint len;
+    uint increment;
     Bool isJavascript = no;
-    
+
     if (!AttrHasValue(attval))
     {
         TY_(ReportAttrError)( doc, node, attval, MISSING_ATTR_VALUE);
@@ -1492,7 +1541,7 @@ void TY_(CheckUrl)( TidyDocImpl* doc, Node *node, AttVal *attval)
     }
 
     p = attval->value;
-    
+
     isJavascript =
         TY_(tmbstrncmp)(p,"javascript:",sizeof("javascript:")-1)==0;
 
@@ -1508,6 +1557,14 @@ void TY_(CheckUrl)( TidyDocImpl* doc, Node *node, AttVal *attval)
             ++escape_count;
     }
 
+    while ( *p != 0 )
+    {
+        if ( !IsURLCodePoint( p, &increment ) )
+            ++bad_codepoint_count;
+         p = p + increment;
+    }
+    p = attval->value;
+
     if ( cfgBool(doc, TidyFixUri) && escape_count )
     {
         Bool hadnonspace = no;
@@ -1557,6 +1614,10 @@ void TY_(CheckUrl)( TidyDocImpl* doc, Node *node, AttVal *attval)
 
         doc->badChars |= BC_INVALID_URI;
     }
+    if ( bad_codepoint_count )
+    {
+        TY_(ReportAttrError)( doc, node, attval, ILLEGAL_URI_CODEPOINT );
+    }
 }
 
 /* RFC 2396, section 4.2 states:
diff --git a/src/language_en.h b/src/language_en.h
index 24b8aa1..cabc39b 100644
--- a/src/language_en.h
+++ b/src/language_en.h
@@ -1821,6 +1821,7 @@ static languageDefinition language_en = { whichPluralForm_en, {
     { ESCAPED_ILLEGAL_URI,          0,   "%s escaping malformed URI reference"                                     }, /* ReportAttrError */
     { FIXED_BACKSLASH,              0,   "%s converting backslash in URI to slash"                                 }, /* ReportAttrError */
     { ID_NAME_MISMATCH,             0,   "%s id and name attribute value mismatch"                                 }, /* ReportAttrError */
+    { ILLEGAL_URI_CODEPOINT,        0,   "%s illegal characters found in URI"                                      }, /* ReportAttrError */
     { ILLEGAL_URI_REFERENCE,        0,   "%s improperly escaped URI reference"                                     }, /* ReportAttrError */
     { INSERTING_AUTO_ATTRIBUTE,     0,   "%s inserting \"%s\" attribute using value \"%s\""                        }, /* ReportAttrError */
     { INVALID_ATTRIBUTE,            0,   "%s attribute name \"%s\" (value=\"%s\") is invalid"                      }, /* ReportAttrError */
diff --git a/src/message.c b/src/message.c
index 2c5587e..48c300f 100755
--- a/src/message.c
+++ b/src/message.c
@@ -525,6 +525,7 @@ void TY_(ReportAttrError)(TidyDocImpl* doc, Node *node, AttVal *av, uint code)
         case ID_NAME_MISMATCH:
         case BACKSLASH_IN_URI:
         case FIXED_BACKSLASH:
+        case ILLEGAL_URI_CODEPOINT:
         case ILLEGAL_URI_REFERENCE:
         case ESCAPED_ILLEGAL_URI:
         case NEWLINE_IN_URI: