diff --git a/vendor/gopkg.in/gcfg.v1/scanner/scanner.go b/vendor/gopkg.in/gcfg.v1/scanner/scanner.go
index 7084c23..1ec8e89 100644
--- a/vendor/gopkg.in/gcfg.v1/scanner/scanner.go
+++ b/vendor/gopkg.in/gcfg.v1/scanner/scanner.go
@@ -148,7 +148,7 @@ func (s *Scanner) scanComment() string {
 }
 
 func isLetter(ch rune) bool {
-	return 'a' <= ch && ch <= 'z' || 'A' <= ch && ch <= 'Z' || ch >= 0x80 && unicode.IsLetter(ch)
+	return 'a' <= ch && ch <= 'z' || 'A' <= ch && ch <= 'Z' || ch == '_' || ch >= 0x80 && unicode.IsLetter(ch)
 }
 
 func isDigit(ch rune) bool {