diff --git a/api/api.go b/api/api.go
index e64738bf..b9e2ef15 100644
--- a/api/api.go
+++ b/api/api.go
@@ -695,16 +695,30 @@ func matchFilterLabels(matchers []*labels.Matcher, sms map[string]string) bool {
 	for _, m := range matchers {
 		v, prs := sms[m.Name]
 		switch m.Type {
-		case labels.MatchNotEqual, labels.MatchNotRegexp:
-			if string(v) == "" && prs {
-				return true
+		case labels.MatchNotRegexp:
+			if string(m.Value) == "^(?:)$" && prs {
+				continue
+			}
+			if !m.Matches(string(v)) {
+				return false
+			}
+		case labels.MatchRegexp:
+			if string(m.Value) == "^(?:)$" && !prs {
+				continue
+			}
+			if !m.Matches(string(v)) {
+				return false
+			}
+		case labels.MatchNotEqual:
+			if string(m.Value) == "" && prs {
+				continue
 			}
 			if !m.Matches(string(v)) {
 				return false
 			}
 		default:
-			if string(v) == "" && !prs {
-				return true
+			if string(m.Value) == "" && !prs {
+				continue
 			}
 			if !prs || !m.Matches(string(v)) {
 				return false