diff --git a/scanner/scanner.go b/scanner/scanner.go
index 4580c89..12d8bbc 100644
--- a/scanner/scanner.go
+++ b/scanner/scanner.go
@@ -7,6 +7,7 @@ import (
 	"io/ioutil"
 	"os"
 	"unicode"
+	"unicode/utf8"
 
 	"github.com/fatih/hcl/token"
 )
@@ -76,6 +77,13 @@ func (s *Scanner) next() rune {
 		return eof
 	}
 
+	if ch == utf8.RuneError && size == 1 {
+		s.srcPos.Column++
+		s.srcPos.Offset += size
+		s.err("illegal UTF-8 encoding")
+		return eof
+	}
+
 	// remember last position
 	s.prevPos = s.srcPos
 	s.lastCharLen = size
@@ -430,6 +438,8 @@ func (s *Scanner) Pos() (pos Position) {
 	return s.tokPos
 }
 
+// err prints the error of any scanning to s.Error function. If the function is
+// not defined, by default it prints them to os.Stderr
 func (s *Scanner) err(msg string) {
 	s.ErrorCount++
 	if s.Error != nil {
@@ -440,22 +450,27 @@ func (s *Scanner) err(msg string) {
 	fmt.Fprintf(os.Stderr, "%s: %s\n", s.srcPos, msg)
 }
 
+// isHexadecimal returns true if the given rune is a letter
 func isLetter(ch rune) bool {
 	return 'a' <= ch && ch <= 'z' || 'A' <= ch && ch <= 'Z' || ch == '_' || ch >= 0x80 && unicode.IsLetter(ch)
 }
 
+// isHexadecimal returns true if the given rune is a decimal digit
 func isDigit(ch rune) bool {
 	return '0' <= ch && ch <= '9' || ch >= 0x80 && unicode.IsDigit(ch)
 }
 
+// isHexadecimal returns true if the given rune is an octan number
 func isOctal(ch rune) bool {
 	return '0' <= ch && ch <= '7'
 }
 
+// isHexadecimal returns true if the given rune is a decimal number
 func isDecimal(ch rune) bool {
 	return '0' <= ch && ch <= '9'
 }
 
+// isHexadecimal returns true if the given rune is an hexadecimal number
 func isHexadecimal(ch rune) bool {
 	return '0' <= ch && ch <= '9' || 'a' <= ch && ch <= 'f' || 'A' <= ch && ch <= 'F'
 }
@@ -465,6 +480,7 @@ func isWhitespace(ch rune) bool {
 	return ch == ' ' || ch == '\t' || ch == '\n' || ch == '\r'
 }
 
+// digitVal returns the integer value of a given octal,decimal or hexadecimal rune
 func digitVal(ch rune) int {
 	switch {
 	case '0' <= ch && ch <= '9':
diff --git a/scanner/scanner_test.go b/scanner/scanner_test.go
index 07951b2..5f97679 100644
--- a/scanner/scanner_test.go
+++ b/scanner/scanner_test.go
@@ -3,6 +3,7 @@ package scanner
 import (
 	"bytes"
 	"fmt"
+	"strings"
 	"testing"
 
 	"github.com/fatih/hcl/token"
@@ -175,7 +176,6 @@ var orderedTokenLists = []string{
 }
 
 func TestPosition(t *testing.T) {
-	// t.SkipNow()
 	// create artifical source code
 	buf := new(bytes.Buffer)
 
@@ -245,6 +245,65 @@ func TestFloat(t *testing.T) {
 	testTokenList(t, tokenLists["float"])
 }
 
+func TestError(t *testing.T) {
+	testError(t, "\x80", "1:1", "illegal UTF-8 encoding", token.EOF)
+	testError(t, "\xff", "1:1", "illegal UTF-8 encoding", token.EOF)
+
+	testError(t, "ab\x80", "1:3", "illegal UTF-8 encoding", token.IDENT)
+	testError(t, "abc\xff", "1:4", "illegal UTF-8 encoding", token.IDENT)
+
+	testError(t, `"ab`+"\x80", "1:4", "illegal UTF-8 encoding", token.STRING)
+	testError(t, `"abc`+"\xff", "1:5", "illegal UTF-8 encoding", token.STRING)
+
+	testError(t, "`ab"+"\x80", "1:4", "illegal UTF-8 encoding", token.STRING)
+	testError(t, "`abc"+"\xff", "1:5", "illegal UTF-8 encoding", token.STRING)
+
+	testError(t, `01238`, "1:6", "illegal octal number", token.NUMBER)
+	testError(t, `01238123`, "1:9", "illegal octal number", token.NUMBER)
+	testError(t, `0x`, "1:3", "illegal hexadecimal number", token.NUMBER)
+	testError(t, `0xg`, "1:3", "illegal hexadecimal number", token.NUMBER)
+	testError(t, `'aa'`, "1:4", "illegal char literal", token.STRING)
+
+	testError(t, `'`, "1:2", "literal not terminated", token.STRING)
+	testError(t, `'`+"\n", "1:2", "literal not terminated", token.STRING)
+	testError(t, `"abc`, "1:5", "literal not terminated", token.STRING)
+	testError(t, `"abc`+"\n", "1:5", "literal not terminated", token.STRING)
+	testError(t, "`abc\n", "2:1", "literal not terminated", token.STRING)
+	testError(t, `/*/`, "1:4", "comment not terminated", token.EOF)
+}
+
+func testError(t *testing.T, src, pos, msg string, tok token.Token) {
+	s, err := NewScanner(strings.NewReader(src))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	errorCalled := false
+	s.Error = func(p Position, m string) {
+		if !errorCalled {
+			if pos != p.String() {
+				t.Errorf("pos = %q, want %q for %q", p, pos, src)
+			}
+
+			if m != msg {
+				t.Errorf("msg = %q, want %q for %q", m, msg, src)
+			}
+			errorCalled = true
+		}
+	}
+
+	tk := s.Scan()
+	if tk != tok {
+		t.Errorf("tok = %s, want %s for %q", tk, tok, src)
+	}
+	if !errorCalled {
+		t.Errorf("error handler not called for %q", src)
+	}
+	if s.ErrorCount == 0 {
+		t.Errorf("count = %d, want > 0 for %q", s.ErrorCount, src)
+	}
+}
+
 func testTokenList(t *testing.T, tokenList []tokenPair) {
 	// create artifical source code
 	buf := new(bytes.Buffer)