diff --git a/.golangci.yml b/.golangci.yml
index 8ea38bd..7c2deec 100644
--- a/.golangci.yml
+++ b/.golangci.yml
@@ -48,7 +48,6 @@ linters:
   - makezero
   - misspell
   - nakedret
-  - nestif
   - nilerr
   - nilnil
   - noctx
@@ -89,6 +88,7 @@ linters:
   - lll
   - maintidx
   - musttag
+  - nestif
   - nlreturn
   - paralleltest
   - tagliatelle
diff --git a/cmd/parse-all/main.go b/cmd/parse-all/main.go
index 1ea74db..5e633f2 100644
--- a/cmd/parse-all/main.go
+++ b/cmd/parse-all/main.go
@@ -15,7 +15,11 @@ import (
 var igcExtensionRx = regexp.MustCompile(`(?i)\.igc\z`)
 
 func run() error {
+	allowInvalidChars := flag.Bool("allow-invalid-chars", true, "allow invalid characters")
 	flag.Parse()
+	options := []igc.ParseOption{
+		igc.WithAllowInvalidChars(*allowInvalidChars),
+	}
 	for _, arg := range flag.Args() {
 		if err := fs.WalkDir(os.DirFS(arg), ".", func(path string, dirEntry fs.DirEntry, err error) error {
 			if err != nil {
@@ -32,7 +36,7 @@ func run() error {
 				return err
 			}
 			defer file.Close()
-			igcFile, err := igc.Parse(file)
+			igcFile, err := igc.Parse(file, options...)
 			if err != nil {
 				return err
 			}
diff --git a/igc.go b/igc.go
index d53266c..bc9b499 100644
--- a/igc.go
+++ b/igc.go
@@ -245,11 +245,11 @@ type IGC struct {
 }
 
 // Parse parses an IGC from r.
-func Parse(r io.Reader) (*IGC, error) {
-	return newParser().parse(r)
+func Parse(r io.Reader, options ...ParseOption) (*IGC, error) {
+	return newParser(options...).parse(r)
 }
 
 // Parse parses an IGC from lines.
-func ParseLines(lines []string) (*IGC, error) {
-	return newParser().parseLines(lines)
+func ParseLines(lines []string, options ...ParseOption) (*IGC, error) {
+	return newParser(options...).parseLines(lines)
 }
diff --git a/igc_test.go b/igc_test.go
index 0623763..559b787 100644
--- a/igc_test.go
+++ b/igc_test.go
@@ -329,7 +329,7 @@ func TestParseLine(t *testing.T) {
 		{
 			name:        "unknown_record_null",
 			line:        "\x00",
-			expectedErr: `1: "\x00": unknown record type`,
+			expectedErr: "1: \"\\x00\": unknown record type\n'\\x00': invalid character",
 		},
 		{
 			name: "empty line",
@@ -953,7 +953,9 @@ func TestParseTestData(t *testing.T) {
 			file, err := os.Open(filepath.Join("testdata", name))
 			assert.NoError(t, err)
 			defer file.Close()
-			igc, err := igc.Parse(file)
+			igc, err := igc.Parse(file,
+				igc.WithAllowInvalidChars(true),
+			)
 			assert.NoError(t, err)
 			assertEqualErrors(t, expectedErrorsByName[name], igc.Errs)
 		})
diff --git a/parser.go b/parser.go
index a57eca6..18651cf 100644
--- a/parser.go
+++ b/parser.go
@@ -55,6 +55,8 @@ func (e unknownRecordTypeError) Error() string {
 }
 
 var (
+	invalidCharsRx = regexp.MustCompile(`([^\x20\x22-\x23\x25-\x29\x2b-\x5b\x5d\x5f-\x7d])`)
+
 	aRecordRx                  = regexp.MustCompile(`\AA([A-Z]{3})(.*)\z`)
 	bRecordRx                  = regexp.MustCompile(`\AB(\d{2})(\d{2})(\d{2})(\d{2})(\d{5})([NS])(\d{3})(\d{5})([EW])([AV])([0-9\-]\d{4})([0-9\-]\d{4})(.*)\z`)
 	cRecordRx                  = regexp.MustCompile(`\AC(\d{2})(\d{5})([NS])(\d{3})(\d{5})([EW])(.*)\z`)
@@ -76,6 +78,7 @@ var (
 )
 
 type parser struct {
+	allowInvalidChars      bool
 	date                   time.Time
 	prevTime               time.Time
 	cRecords               []Record
@@ -92,8 +95,16 @@ type parser struct {
 	kRecordAdditions       []BKRecordAddition
 }
 
-func newParser() *parser {
-	return &parser{
+type ParseOption func(*parser)
+
+func WithAllowInvalidChars(allowInvalidChars bool) ParseOption {
+	return func(p *parser) {
+		p.allowInvalidChars = allowInvalidChars
+	}
+}
+
+func newParser(options ...ParseOption) *parser {
+	p := &parser{
 		bRecordsAdditionsByTLC: make(map[string]*BKRecordAddition),
 		latMinMul:              1,
 		latMinDiv:              6e4,
@@ -101,6 +112,10 @@ func newParser() *parser {
 		lonMinDiv:              6e4,
 		fracSecondMul:          1e9,
 	}
+	for _, o := range options {
+		o(p)
+	}
+	return p
 }
 
 func (p *parser) parse(r io.Reader) (*IGC, error) {
@@ -158,6 +173,22 @@ func (p *parser) parseLines(lines []string) (*IGC, error) {
 		default:
 			err = unknownRecordTypeError(line[0])
 		}
+		if !p.allowInvalidChars {
+			if match := invalidCharsRx.FindStringSubmatch(lineStr); match != nil {
+				invalidChar := match[1][0]
+				var invalidCharErr error
+				if '\x20' <= invalidChar && invalidChar <= '\x7f' {
+					invalidCharErr = fmt.Errorf("'%c': invalid character", invalidChar)
+				} else {
+					invalidCharErr = fmt.Errorf("'\\x%02x': invalid character", invalidChar)
+				}
+				if err == nil {
+					err = invalidCharErr
+				} else {
+					err = errors.Join(err, invalidCharErr)
+				}
+			}
+		}
 		records = append(records, record)
 		if err != nil {
 			errs = append(errs, &Error{
diff --git a/parser_test.go b/parser_test.go
index 6431ed4..eb40a2a 100644
--- a/parser_test.go
+++ b/parser_test.go
@@ -69,3 +69,50 @@ func TestIntPow(t *testing.T) {
 		})
 	}
 }
+
+func TestReservedCharacters(t *testing.T) {
+	for c, expected := range map[byte]bool{
+		'\r':   true,
+		'\n':   true,
+		' ':    false,
+		'!':    true,
+		'"':    false,
+		'#':    false,
+		'$':    true,
+		'%':    false,
+		'&':    false,
+		'\'':   false,
+		'(':    false,
+		')':    false,
+		'0':    false,
+		'9':    false,
+		':':    false,
+		';':    false,
+		'<':    false,
+		'=':    false,
+		'>':    false,
+		'?':    false,
+		'@':    false,
+		'A':    false,
+		'Z':    false,
+		'[':    false,
+		'\\':   true,
+		']':    false,
+		'^':    true,
+		'_':    false,
+		'`':    false,
+		'a':    false,
+		'z':    false,
+		'{':    false,
+		'|':    false,
+		'}':    false,
+		'~':    true,
+		'*':    true,
+		'\x80': true,
+		'\xff': true,
+	} {
+		t.Run(string(c), func(t *testing.T) {
+			assert.Equal(t, expected, invalidCharsRx.MatchString(string(c)))
+		})
+	}
+}