diff --git a/pkg/labels/regexp.go b/pkg/labels/regexp.go
index 6c8a131011..705d8cc5f4 100644
--- a/pkg/labels/regexp.go
+++ b/pkg/labels/regexp.go
@@ -115,9 +115,7 @@ func findSetMatchesFromConcat(re *syntax.Regexp, base string) []string {
 	if len(re.Sub) == 0 {
 		return nil
 	}
-	for _, sub := range re.Sub {
-		clearCapture(sub)
-	}
+	clearCapture(re.Sub...)
 	matches := findSetMatches(re.Sub[0], base)
 	if matches == nil {
 		return nil
diff --git a/pkg/labels/regexp_test.go b/pkg/labels/regexp_test.go
index 2dba236710..abaa6b5d3f 100644
--- a/pkg/labels/regexp_test.go
+++ b/pkg/labels/regexp_test.go
@@ -116,6 +116,7 @@ func TestFindSetMatches(t *testing.T) {
 		{"bar|b|buzz", []string{"bar", "b", "buzz"}},
 		// Simple sets containing escaped characters.
 		{"fo\\.o|bar\\?|\\^baz", []string{"fo.o", "bar?", "^baz"}},
+		// using charclass
 		{"[abc]d", []string{"ad", "bd", "cd"}},
 		// high low charset different => A(B[CD]|EF)|BC[XY]
 		{"ABC|ABD|AEF|BCX|BCY", []string{"ABC", "ABD", "AEF", "BCX", "BCY"}},