diff --git a/src/lib/go/parser/parser.go b/src/lib/go/parser/parser.go
index 37fd431eda..622268d1ec 100644
--- a/src/lib/go/parser/parser.go
+++ b/src/lib/go/parser/parser.go
@@ -1921,6 +1921,15 @@ func readSource(src interface{}) ([]byte, os.Error) {
 }
 
 
+// scannerMode returns the scanner mode bits given the parser's mode bits.
+func scannerMode(mode uint) uint {
+	if mode & ParseComments != 0 {
+		return scanner.ScanComments;
+	}
+	return 0;
+}
+
+
 // Parse parses a Go program.
 //
 // The program source src may be provided in a variety of formats. At the
@@ -1944,7 +1953,7 @@ func Parse(src interface{}, mode uint) (*ast.Program, os.Error) {
 	// initialize parser state
 	var p parser;
 	p.errors.Init(0);
-	p.scanner.Init(data, &p, mode & ParseComments != 0);
+	p.scanner.Init(data, &p, scannerMode(mode));
 	p.mode = mode;
 	p.trace = mode & Trace != 0;  // for convenience (p.trace is used frequently)
 	p.comments.Init(0);
diff --git a/src/lib/go/scanner/scanner.go b/src/lib/go/scanner/scanner.go
index 7cfc48d88f..a90e6f2592 100644
--- a/src/lib/go/scanner/scanner.go
+++ b/src/lib/go/scanner/scanner.go
@@ -35,7 +35,7 @@ type Scanner struct {
 	// immutable state
 	src []byte;  // source
 	err ErrorHandler;  // error reporting; or nil
-	scan_comments bool;  // if set, comments are reported as tokens
+	mode uint;  // scanning mode
 
 	// scanning state
 	pos token.Position;  // previous reading position (position before ch)
@@ -72,19 +72,26 @@ func (S *Scanner) next() {
 }
 
 
+// The mode parameter to the Init function is a set of flags (or 0).
+// They control scanner behavior.
+//
+const (
+	ScanComments = 1 << iota;  // return comments as COMMENT tokens
+	AllowIllegalChars;  // do not report an error for illegal chars
+)
+
+
 // Init prepares the scanner S to tokenize the text src. Calls to Scan
 // will use the error handler err if they encounter a syntax error and
 // err is not nil. Also, for each error encountered, the Scanner field
-// ErrorCount is incremented by one. The boolean scan_comments specifies
-// whether comments should be recognized and returned by Scan as COMMENT
-// tokens. If scan_comments is false, they are treated as white space and
-// ignored.
+// ErrorCount is incremented by one. The mode parameter determines how
+// comments and illegal characters are handled.
 //
-func (S *Scanner) Init(src []byte, err ErrorHandler, scan_comments bool) {
+func (S *Scanner) Init(src []byte, err ErrorHandler, mode uint) {
 	// Explicitly initialize all fields since a scanner may be reused.
 	S.src = src;
 	S.err = err;
-	S.scan_comments = scan_comments;
+	S.mode = mode;
 	S.pos = token.Position{0, 1, 0};
 	S.offset = 0;
 	S.ErrorCount = 0;
@@ -441,7 +448,7 @@ scan_again:
 			if S.ch == '/' || S.ch == '*' {
 				S.scanComment(pos);
 				tok = token.COMMENT;
-				if !S.scan_comments {
+				if S.mode & ScanComments == 0 {
 					goto scan_again;
 				}
 			} else {
@@ -467,7 +474,10 @@ scan_again:
 				tok = S.switch3(token.AND, token.AND_ASSIGN, '&', token.LAND);
 			}
 		case '|': tok = S.switch3(token.OR, token.OR_ASSIGN, '|', token.LOR);
-		default: S.error(pos, "illegal character " + charString(ch));
+		default:
+			if S.mode & AllowIllegalChars == 0 {
+				S.error(pos, "illegal character " + charString(ch));
+			}
 		}
 	}
 
@@ -481,9 +491,9 @@ scan_again:
 // false (usually when the token value is token.EOF). The result is the number
 // of errors encountered.
 //
-func Tokenize(src []byte, err ErrorHandler, scan_comments bool, f func (pos token.Position, tok token.Token, lit []byte) bool) int {
+func Tokenize(src []byte, err ErrorHandler, mode uint, f func (pos token.Position, tok token.Token, lit []byte) bool) int {
 	var s Scanner;
-	s.Init(src, err, scan_comments);
+	s.Init(src, err, mode);
 	for f(s.Scan()) {
 		// action happens in f
 	}
diff --git a/src/lib/go/scanner/scanner_test.go b/src/lib/go/scanner/scanner_test.go
index 19fe9864f1..0defece8b0 100644
--- a/src/lib/go/scanner/scanner_test.go
+++ b/src/lib/go/scanner/scanner_test.go
@@ -188,7 +188,7 @@ func TestScan(t *testing.T) {
 	// verify scan
 	index := 0;
 	eloc := token.Position{0, 1, 1};
-	nerrors := scanner.Tokenize(io.StringBytes(src), &TestErrorHandler{t}, true,
+	nerrors := scanner.Tokenize(io.StringBytes(src), &TestErrorHandler{t}, scanner.ScanComments,
 		func (pos token.Position, tok token.Token, litb []byte) bool {
 			e := elt{token.EOF, "", special};
 			if index < len(tokens) {
@@ -234,7 +234,7 @@ func TestInit(t *testing.T) {
 	var s scanner.Scanner;
 
 	// 1st init
-	s.Init(io.StringBytes("if true { }"), nil, false);
+	s.Init(io.StringBytes("if true { }"), nil, 0);
 	s.Scan();  // if
 	s.Scan();  // true
 	pos, tok, lit := s.Scan();  // {
@@ -243,7 +243,7 @@ func TestInit(t *testing.T) {
 	}
 
 	// 2nd init
-	s.Init(io.StringBytes("go true { ]"), nil, false);
+	s.Init(io.StringBytes("go true { ]"), nil, 0);
 	pos, tok, lit = s.Scan();  // go
 	if tok != token.GO {
 		t.Errorf("bad token: got %s, expected %s", tok.String(), token.GO);
@@ -253,3 +253,24 @@ func TestInit(t *testing.T) {
 		t.Errorf("found %d errors", s.ErrorCount);
 	}
 }
+
+
+func TestIllegalChars(t *testing.T) {
+	var s scanner.Scanner;
+
+	const src = "*?*$*@*";
+	s.Init(io.StringBytes(src), &TestErrorHandler{t}, scanner.AllowIllegalChars);
+	for offs, ch := range src {
+		pos, tok, lit := s.Scan();
+		if pos.Offset != offs {
+			t.Errorf("bad position for %s: got %d, expected %d", string(lit), pos.Offset, offs);
+		}
+		if tok == token.ILLEGAL && string(lit) != string(ch) {
+			t.Errorf("bad token: got %s, expected %s", string(lit), string(ch));
+		}
+	}
+
+	if s.ErrorCount != 0 {
+		t.Errorf("found %d errors", s.ErrorCount);
+	}
+}