diff --git a/json/lex.go b/json/lex.go
index 750c0aa..0c1299c 100644
--- a/json/lex.go
+++ b/json/lex.go
@@ -74,10 +74,50 @@ func (x *jsonLex) Lex(yylval *jsonSymType) int {
 		case '"':
 			return x.lexString(yylval)
 		default:
-			x.createErr(fmt.Sprintf("unexpected character: %c", c))
+			x.backup()
+			return x.lexId(yylval)
+		}
+	}
+}
+
+// lexId lexes an identifier
+func (x *jsonLex) lexId(yylval *jsonSymType) int {
+	var b bytes.Buffer
+	first := true
+	for {
+		c := x.next()
+		if c == lexEOF {
+			break
+		}
+
+		if !unicode.IsDigit(c) && !unicode.IsLetter(c) && c != '_' && c != '-' {
+			x.backup()
+
+			if first {
+				x.createErr("Invalid identifier")
+				return lexEOF
+			}
+
+			break
+		}
+
+		first = false
+		if _, err := b.WriteRune(c); err != nil {
 			return lexEOF
 		}
 	}
+
+	switch v := b.String(); v {
+	case "true":
+		return TRUE
+	case "false":
+		return FALSE
+	case "null":
+		return NULL
+	default:
+		x.createErr(fmt.Sprintf("Invalid identifier: %s", v))
+		return lexEOF
+	}
 }
 
 // lexNumber lexes out a number
diff --git a/json/test-fixtures/types.json b/json/test-fixtures/types.json
index 19b05a8..9a142a6 100644
--- a/json/test-fixtures/types.json
+++ b/json/test-fixtures/types.json
@@ -3,5 +3,8 @@
 	"bar": 7,
 	"baz": [1,2,3],
 	"foo": -12,
-	"bar": 3.14159
+	"bar": 3.14159,
+    "foo": true,
+    "bar": false,
+    "foo": null
 }