diff --git a/model/labels/regexp_test.go b/model/labels/regexp_test.go
index 41160cc05..e9f12d7b6 100644
--- a/model/labels/regexp_test.go
+++ b/model/labels/regexp_test.go
@@ -37,6 +37,7 @@ var (
 		".*foo",
 		"^.*foo$",
 		"^.+foo$",
+		".?",
 		".*",
 		".+",
 		"foo.+",
@@ -89,6 +90,12 @@ var (
 
 		// Values matching / not matching the test regexps on long alternations.
 		"zQPbMkNO", "zQPbMkNo", "jyyfj00j0061", "jyyfj00j006", "jyyfj00j00612", "NNSPdvMi", "NNSPdvMiXXX", "NNSPdvMixxx", "nnSPdvMi", "nnSPdvMiXXX",
+
+		// Invalid utf8
+		"\xfefoo",
+		"foo\xfe",
+		"\xfd",
+		"\xff\xff",
 	}
 )