diff --git a/debug/debug.go b/debug/debug.go
index 7a756ae..24c1386 100644
--- a/debug/debug.go
+++ b/debug/debug.go
@@ -92,7 +92,7 @@ func dumpAttrs(w io.Writer, c *Config, p *radius.Packet) {
 				case dictionary.AttributeInteger:
 					switch len(attr) {
 					case 4:
-						intVal := int(binary.BigEndian.Uint32(attr))
+						intVal := uint(binary.BigEndian.Uint32(attr))
 						if dictAttr != nil {
 							var matchedNames []string
 							for _, value := range dictionary.ValuesByAttribute(searchValues, dictAttr.Name) {
@@ -106,7 +106,7 @@ func dumpAttrs(w io.Writer, c *Config, p *radius.Packet) {
 								break
 							}
 						}
-						attrStr = strconv.Itoa(intVal)
+						attrStr = strconv.FormatUint(uint64(intVal), 10)
 					case 8:
 						attrStr = strconv.Itoa(int(binary.BigEndian.Uint64(attr)))
 					}
diff --git a/dictionary/dictionary.go b/dictionary/dictionary.go
index 057d77b..e7fd7bc 100644
--- a/dictionary/dictionary.go
+++ b/dictionary/dictionary.go
@@ -184,6 +184,37 @@ func (a *Attribute) Equals(o *Attribute) bool {
 	return true
 }
 
+func normalizedType(t AttributeType) AttributeType {
+	if t == AttributeString {
+		return AttributeOctets
+	}
+
+	return t
+}
+
+func (a *Attribute) MostlyEquals(o *Attribute) bool {
+	if a == o {
+		return true
+	}
+	if a == nil || o == nil {
+		return false
+	}
+
+	if a.Name != o.Name || !a.OID.Equals(o.OID) {
+		return false
+	}
+
+	if normalizedType(a.Type) != normalizedType(o.Type) {
+		return false
+	}
+
+	if a.FlagEncrypt != o.FlagEncrypt || a.FlagHasTag != o.FlagHasTag || a.FlagConcat != o.FlagConcat {
+		return false
+	}
+
+	return true
+}
+
 func (a *Attribute) GoString() string {
 	var b bytes.Buffer
 	b.WriteString("&dictionary.Attribute{")
@@ -213,7 +244,7 @@ func (a *Attribute) GoString() string {
 type Value struct {
 	Attribute string
 	Name      string
-	Number    int
+	Number    uint
 }
 
 type Vendor struct {
@@ -227,6 +258,18 @@ type Vendor struct {
 	Values     []*Value
 }
 
+func (a *Vendor) Equals(b *Vendor) bool {
+	if a == b {
+		return true
+	}
+
+	if a == nil || b == nil {
+		return false
+	}
+
+	return a.Name == b.Name && a.Number == a.Number
+}
+
 func (v *Vendor) GetTypeOctets() int {
 	if v.TypeOctets == nil {
 		return 1
diff --git a/dictionary/parser.go b/dictionary/parser.go
index d25b5de..622d019 100644
--- a/dictionary/parser.go
+++ b/dictionary/parser.go
@@ -40,7 +40,8 @@ type Parser struct {
 
 	// IgnoreIdenticalAttributes specifies whether identical attributes are
 	// ignored, rather than a parse error being emitted.
-	IgnoreIdenticalAttributes bool
+	IgnoreIdenticalAttributes  bool
+	IgnoreUnknownAttributeType bool
 }
 
 func (p *Parser) Parse(f File) (*Dictionary, error) {
@@ -62,6 +63,7 @@ func (p *Parser) parse(dict *Dictionary, parsedFiles map[string]struct{}, f File
 	lineNo := 1
 	for ; s.Scan(); lineNo++ {
 		line := s.Text()
+		line = strings.TrimLeft(line, " ")
 		if idx := strings.IndexByte(line, '#'); idx >= 0 {
 			line = line[:idx]
 		}
@@ -74,6 +76,12 @@ func (p *Parser) parse(dict *Dictionary, parsedFiles map[string]struct{}, f File
 		case (len(fields) == 4 || len(fields) == 5) && fields[0] == "ATTRIBUTE":
 			attr, err := p.parseAttribute(fields)
 			if err != nil {
+				switch err.(type) {
+				case *UnknownAttributeTypeError:
+					if p.IgnoreUnknownAttributeType {
+						continue
+					}
+				}
 				return &ParseError{
 					Inner: err,
 					File:  f,
@@ -88,7 +96,7 @@ func (p *Parser) parse(dict *Dictionary, parsedFiles map[string]struct{}, f File
 				existing = AttributeByName(vendorBlock.Attributes, attr.Name)
 			}
 			if existing != nil {
-				if p.IgnoreIdenticalAttributes && attr.Equals(existing) {
+				if p.IgnoreIdenticalAttributes && attr.MostlyEquals(existing) {
 					break
 				}
 				return &ParseError{
@@ -134,18 +142,10 @@ func (p *Parser) parse(dict *Dictionary, parsedFiles map[string]struct{}, f File
 				}
 			}
 
-			if existing := vendorByNameOrNumber(dict.Vendors, vendor.Name, vendor.Number); existing != nil {
-				return &ParseError{
-					Inner: &DuplicateVendorError{
-						Vendor: vendor,
-					},
-					File: f,
-					Line: lineNo,
-				}
+			if existing := vendorByNameOrNumber(dict.Vendors, vendor.Name, vendor.Number); existing == nil || !vendor.Equals(existing) {
+				dict.Vendors = append(dict.Vendors, vendor)
 			}
 
-			dict.Vendors = append(dict.Vendors, vendor)
-
 		case len(fields) == 2 && fields[0] == "BEGIN-VENDOR":
 			// TODO: support RFC 6929 extended VSA?
 
@@ -276,6 +276,16 @@ func (p *Parser) ParseFile(filename string) (*Dictionary, error) {
 
 func parseOID(s string) OID {
 	var o OID
+	if len(s) > 2 && s[0] == '0' && (s[1] == 'x' || s[1] == 'X') {
+		num, err := strconv.ParseInt(s[2:], 16, 32)
+		if err != nil {
+			return nil
+		}
+
+		o = append(o, int(num))
+		return o
+	}
+
 	for i, ch := range s {
 		switch ch {
 		case '.':
@@ -405,6 +415,8 @@ func (p *Parser) parseAttribute(f []string) (*Attribute, error) {
 					Valid: true,
 					Bool:  true,
 				}
+			case f == "virtual":
+				continue
 			default:
 				return nil, &UnknownAttributeFlagError{
 					Flag: f,
@@ -424,11 +436,18 @@ func (p *Parser) parseValue(f []string) (*Value, error) {
 		Name:      f[2],
 	}
 
-	number, err := strconv.ParseInt(f[3], 10, 32)
+	numStr := f[3]
+	base := 10
+	if len(numStr) > 2 && (numStr[0] == '0' && (numStr[1] == 'x' || numStr[1] == 'X')) {
+		base = 16
+		numStr = numStr[2:]
+	}
+
+	number, err := strconv.ParseUint(numStr, base, 32)
 	if err != nil {
 		return nil, err
 	}
-	value.Number = int(number)
+	value.Number = uint(number)
 
 	return value, nil
 }
@@ -450,7 +469,7 @@ func (p *Parser) parseVendor(f []string) (*Vendor, error) {
 		// "format=t,l"
 		// t ∈ [1, 2, 4]
 		// l ∈ [0, 1, 2]
-		if !strings.HasPrefix(f[3], "format=") || len(f[3]) != 10 || f[3][8] != ',' || (f[3][7] != '1' && f[3][7] != '2' && f[3][7] != '4') || (f[3][9] < '0' && f[3][9] > '2') {
+		if !strings.HasPrefix(f[3], "format=") || len(f[3]) < 10 || f[3][8] != ',' || (f[3][7] != '1' && f[3][7] != '2' && f[3][7] != '4') || (f[3][9] < '0' || f[3][9] > '2') {
 			return nil, &InvalidVendorFormatError{
 				Format: f[3],
 			}
diff --git a/dictionary/parser_test.go b/dictionary/parser_test.go
index 58717a2..eff8415 100644
--- a/dictionary/parser_test.go
+++ b/dictionary/parser_test.go
@@ -80,6 +80,11 @@ func TestParser(t *testing.T) {
 				Name:      "Half",
 				Number:    2,
 			},
+			{
+				Attribute: "Mode",
+				Name:      "Quarter",
+				Number:    4,
+			},
 		},
 	}
 
diff --git a/dictionary/testdata/simple.dictionary b/dictionary/testdata/simple.dictionary
index 01b82c6..37f4229 100644
--- a/dictionary/testdata/simple.dictionary
+++ b/dictionary/testdata/simple.dictionary
@@ -1,8 +1,12 @@
 ATTRIBUTE User-Name 1 string
 ATTRIBUTE User-Password 2 octets encrypt=1
 
+#Skip comment
+   #Skip comment with spaces in front
+
 ATTRIBUTE Mode 127 integer
 VALUE Mode Full 1
 VALUE Mode Half 2
+VALUE Mode Quarter 0x4
 
 ATTRIBUTE ARAP-Challenge-Response 84 octets[8]
diff --git a/dictionarygen/attributes.go b/dictionarygen/attributes.go
index 0d27a9d..44b52e5 100644
--- a/dictionarygen/attributes.go
+++ b/dictionarygen/attributes.go
@@ -873,7 +873,7 @@ func (g *Generator) genAttributeInteger(w io.Writer, attr *dictionary.Attribute,
 		p(w, `const (`)
 		for _, value := range values {
 			valueIdent := identifier(value.Name)
-			p(w, `	`, ident, `_Value_`, valueIdent, ` `, ident, ` = `, strconv.Itoa(value.Number))
+			p(w, `	`, ident, `_Value_`, valueIdent, ` `, ident, ` = `, strconv.FormatUint(uint64(value.Number), 10))
 		}
 		p(w, `)`)
 	}
diff --git a/dictionarygen/generator.go b/dictionarygen/generator.go
index 11b8955..c7658b1 100644
--- a/dictionarygen/generator.go
+++ b/dictionarygen/generator.go
@@ -292,7 +292,7 @@ func (g *Generator) Generate(dict *dictionary.Dictionary) ([]byte, error) {
 		for _, value := range exAttr.Values {
 			attrIdent := identifier(value.Attribute)
 			valueIdent := identifier(value.Name)
-			p(&w, `	`, attrIdent, `_Value_`, valueIdent, ` `, attrIdent, ` = `, strconv.Itoa(value.Number))
+			p(&w, `	`, attrIdent, `_Value_`, valueIdent, ` `, attrIdent, ` = `, strconv.FormatUint(uint64(value.Number), 10))
 		}
 		p(&w, `)`)
 	}