diff --git a/conf/lex.go b/conf/lex.go
index 3f6ae1c6..8a7ce5f7 100644
--- a/conf/lex.go
+++ b/conf/lex.go
@@ -684,8 +684,10 @@ func lexMapEnd(lx *lexer) stateFn {
 
 // Checks if the unquoted string was actually a boolean
 func (lx *lexer) isBool() bool {
-	str := lx.input[lx.start:lx.pos]
-	return str == "true" || str == "false" || str == "TRUE" || str == "FALSE"
+	str := strings.ToLower(lx.input[lx.start:lx.pos])
+	return str == "true" || str == "false" ||
+		str == "on" || str == "off" ||
+		str == "yes" || str == "no"
 }
 
 // Check if the unquoted string is a variable reference, starting with $.
diff --git a/conf/parse.go b/conf/parse.go
index fa7292db..32767c48 100644
--- a/conf/parse.go
+++ b/conf/parse.go
@@ -183,10 +183,10 @@ func (p *parser) processItem(it item) error {
 		}
 		p.setValue(num)
 	case itemBool:
-		switch it.val {
-		case "true":
+		switch strings.ToLower(it.val) {
+		case "true", "yes", "on":
 			p.setValue(true)
-		case "false":
+		case "false", "no", "off":
 			p.setValue(false)
 		default:
 			return fmt.Errorf("Expected boolean value, but got '%s'.", it.val)
diff --git a/conf/parse_test.go b/conf/parse_test.go
index d675cca5..6992c113 100644
--- a/conf/parse_test.go
+++ b/conf/parse_test.go
@@ -35,6 +35,17 @@ func TestSimpleTopLevel(t *testing.T) {
 	test(t, "foo='1'; bar=2.2; baz=true; boo=22", ex)
 }
 
+func TestBools(t *testing.T) {
+	ex := map[string]interface{}{
+		"foo": true,
+	}
+	test(t, "foo=true", ex)
+	test(t, "foo=TRUE", ex)
+	test(t, "foo=true", ex)
+	test(t, "foo=yes", ex)
+	test(t, "foo=on", ex)
+}
+
 var varSample = `
   index = 22
   foo = $index