diff --git a/src/pkg/mime/multipart/formdata.go b/src/pkg/mime/multipart/formdata.go
index 198ab515b8..5f32865659 100644
--- a/src/pkg/mime/multipart/formdata.go
+++ b/src/pkg/mime/multipart/formdata.go
@@ -41,10 +41,7 @@ func (r *multiReader) ReadForm(maxMemory int64) (f *Form, err os.Error) {
 		if name == "" {
 			continue
 		}
-		var filename string
-		if p.dispositionParams != nil {
-			filename = p.dispositionParams["filename"]
-		}
+		filename := p.FileName()
 
 		var b bytes.Buffer
 
diff --git a/src/pkg/mime/multipart/multipart.go b/src/pkg/mime/multipart/multipart.go
index 839a72f9c3..9affa11261 100644
--- a/src/pkg/mime/multipart/multipart.go
+++ b/src/pkg/mime/multipart/multipart.go
@@ -26,6 +26,8 @@ import (
 
 var headerRegexp *regexp.Regexp = regexp.MustCompile("^([a-zA-Z0-9\\-]+): *([^\r\n]+)")
 
+var emptyParams = make(map[string]string)
+
 // Reader is an iterator over parts in a MIME multipart body.
 // Reader's underlying parser consumes its input as needed.  Seeking
 // isn't supported.
@@ -51,6 +53,7 @@ type Part struct {
 	buffer *bytes.Buffer
 	mr     *multiReader
 
+	disposition       string
 	dispositionParams map[string]string
 }
 
@@ -59,21 +62,33 @@ type Part struct {
 func (p *Part) FormName() string {
 	// See http://tools.ietf.org/html/rfc2183 section 2 for EBNF
 	// of Content-Disposition value format.
-	if p.dispositionParams != nil {
-		return p.dispositionParams["name"]
+	if p.dispositionParams == nil {
+		p.parseContentDisposition()
 	}
-	v := p.Header.Get("Content-Disposition")
-	if v == "" {
+	if p.disposition != "form-data" {
 		return ""
 	}
-	if d, params := mime.ParseMediaType(v); d != "form-data" {
-		return ""
-	} else {
-		p.dispositionParams = params
-	}
 	return p.dispositionParams["name"]
 }
 
+
+// FileName returns the filename parameter of the Part's
+// Content-Disposition header.
+func (p *Part) FileName() string {
+	if p.dispositionParams == nil {
+		p.parseContentDisposition()
+	}
+	return p.dispositionParams["filename"]
+}
+
+func (p *Part) parseContentDisposition() {
+	v := p.Header.Get("Content-Disposition")
+	p.disposition, p.dispositionParams = mime.ParseMediaType(v)
+	if p.dispositionParams == nil {
+		p.dispositionParams = emptyParams
+	}
+}
+
 // NewReader creates a new multipart Reader reading from r using the
 // given MIME boundary.
 func NewReader(reader io.Reader, boundary string) Reader {
diff --git a/src/pkg/mime/multipart/multipart_test.go b/src/pkg/mime/multipart/multipart_test.go
index 05f4871472..8222fbd8a4 100644
--- a/src/pkg/mime/multipart/multipart_test.go
+++ b/src/pkg/mime/multipart/multipart_test.go
@@ -56,24 +56,25 @@ func expectEq(t *testing.T, expected, actual, what string) {
 		what, escapeString(actual), len(actual), escapeString(expected), len(expected))
 }
 
-func TestFormName(t *testing.T) {
-	p := new(Part)
-	p.Header = make(map[string][]string)
-	tests := [...][2]string{
-		{`form-data; name="foo"`, "foo"},
-		{` form-data ; name=foo`, "foo"},
-		{`FORM-DATA;name="foo"`, "foo"},
-		{` FORM-DATA ; name="foo"`, "foo"},
-		{` FORM-DATA ; name="foo"`, "foo"},
-		{` FORM-DATA ; name=foo`, "foo"},
-		{` FORM-DATA ; filename="foo.txt"; name=foo; baz=quux`, "foo"},
+func TestNameAccessors(t *testing.T) {
+	tests := [...][3]string{
+		{`form-data; name="foo"`, "foo", ""},
+		{` form-data ; name=foo`, "foo", ""},
+		{`FORM-DATA;name="foo"`, "foo", ""},
+		{` FORM-DATA ; name="foo"`, "foo", ""},
+		{` FORM-DATA ; name="foo"`, "foo", ""},
+		{` FORM-DATA ; name=foo`, "foo", ""},
+		{` FORM-DATA ; filename="foo.txt"; name=foo; baz=quux`, "foo", "foo.txt"},
+		{` not-form-data ; filename="bar.txt"; name=foo; baz=quux`, "", "bar.txt"},
 	}
-	for _, test := range tests {
+	for i, test := range tests {
+		p := &Part{Header: make(map[string][]string)}
 		p.Header.Set("Content-Disposition", test[0])
-		expected := test[1]
-		actual := p.FormName()
-		if actual != expected {
-			t.Errorf("expected \"%s\"; got: \"%s\"", expected, actual)
+		if g, e := p.FormName(), test[1]; g != e {
+			t.Errorf("test %d: FormName() = %q; want %q", i, g, e)
+		}
+		if g, e := p.FileName(), test[2]; g != e {
+			t.Errorf("test %d: FileName() = %q; want %q", i, g, e)
 		}
 	}
 }