diff --git a/uri.go b/uri.go
index 43060de..0f6bc04 100644
--- a/uri.go
+++ b/uri.go
@@ -213,6 +213,11 @@ func (u *URI) SetHostBytes(host []byte) {
 }
 
 // Parse initializes URI from the given host and uri.
+//
+// host may be nil. In this case uri must contain fully qualified uri,
+// i.e. with scheme and host. http is assumed if scheme is omitted.
+//
+// uri may contain e.g. RequestURI without scheme and host if host is non-empty.
 func (u *URI) Parse(host, uri []byte) {
 	u.parse(host, uri, nil)
 }
@@ -369,6 +374,8 @@ func (u *URI) LastPathSegment() []byte {
 //
 //     * Absolute, i.e. http://foobar.com/aaa/bb?cc . In this case the original
 //       uri is replaced by newURI.
+//     * Absolute without scheme, i.e. //foobar.com/aaa/bb?cc. In this case
+//       the original scheme is preserved.
 //     * Missing host, i.e. /aaa/bb?cc . In this case only RequestURI part
 //       of the original uri is replaced.
 //     * Relative path, i.e.  xx?yy=abc . In this case the original RequestURI
@@ -383,6 +390,8 @@ func (u *URI) Update(newURI string) {
 //
 //     * Absolute, i.e. http://foobar.com/aaa/bb?cc . In this case the original
 //       uri is replaced by newURI.
+//     * Absolute without scheme, i.e. //foobar.com/aaa/bb?cc. In this case
+//       the original scheme is preserved.
 //     * Missing host, i.e. /aaa/bb?cc . In this case only RequestURI part
 //       of the original uri is replaced.
 //     * Relative path, i.e.  xx?yy=abc . In this case the original RequestURI
diff --git a/uri_test.go b/uri_test.go
index b86bb48..c10d21b 100644
--- a/uri_test.go
+++ b/uri_test.go
@@ -115,6 +115,7 @@ func TestURIUpdate(t *testing.T) {
 
 	// uri without scheme
 	testURIUpdate(t, "https://foo.bar/baz", "//aaa.bbb/cc?dd", "https://aaa.bbb/cc?dd")
+	testURIUpdate(t, "http://foo.bar/baz", "//aaa.bbb/cc?dd", "http://aaa.bbb/cc?dd")
 }
 
 func testURIUpdate(t *testing.T, base, update, result string) {
@@ -228,18 +229,25 @@ func testURIFullURI(t *testing.T, scheme, host, path, hash string, args *Args, e
 }
 
 func TestURIParseNilHost(t *testing.T) {
-	testURIParseScheme(t, "http://google.com/foo?bar#baz", "http")
-	testURIParseScheme(t, "HTtP://google.com/", "http")
-	testURIParseScheme(t, "://google.com/", "http")
-	testURIParseScheme(t, "fTP://aaa.com", "ftp")
-	testURIParseScheme(t, "httPS://aaa.com", "https")
+	testURIParseScheme(t, "http://google.com/foo?bar#baz", "http", "google.com", "/foo?bar#baz")
+	testURIParseScheme(t, "HTtP://google.com/", "http", "google.com", "/")
+	testURIParseScheme(t, "://google.com/xyz", "http", "google.com", "/xyz")
+	testURIParseScheme(t, "//google.com/foobar", "http", "google.com", "/foobar")
+	testURIParseScheme(t, "fTP://aaa.com", "ftp", "aaa.com", "/")
+	testURIParseScheme(t, "httPS://aaa.com", "https", "aaa.com", "/")
 }
 
-func testURIParseScheme(t *testing.T, uri, expectedScheme string) {
+func testURIParseScheme(t *testing.T, uri, expectedScheme, expectedHost, expectedRequestURI string) {
 	var u URI
 	u.Parse(nil, []byte(uri))
 	if string(u.Scheme()) != expectedScheme {
-		t.Fatalf("Unexpected scheme %q. Expected %q for uri %q", u.Scheme(), expectedScheme, uri)
+		t.Fatalf("Unexpected scheme %q. Expecting %q for uri %q", u.Scheme(), expectedScheme, uri)
+	}
+	if string(u.Host()) != expectedHost {
+		t.Fatalf("Unexepcted host %q. Expecting %q for uri %q", u.Host(), expectedHost, uri)
+	}
+	if string(u.RequestURI()) != expectedRequestURI {
+		t.Fatalf("Unexepcted requestURI %q. Expecting %q for uri %q", u.RequestURI(), expectedRequestURI, uri)
 	}
 }