diff --git a/pkg/custom-provider/series_registry_test.go b/pkg/custom-provider/series_registry_test.go
index 09e440a7..7dd5352d 100644
--- a/pkg/custom-provider/series_registry_test.go
+++ b/pkg/custom-provider/series_registry_test.go
@@ -164,7 +164,7 @@ var _ = Describe("Series Registry", func() {
 				resourceNames:  []string{"somepod1", "somepod2"},
 				metricSelector: labels.Everything(),
 
-				expectedQuery: "sum(container_some_usage{namespace=\"somens\",pod=~\"somepod1|somepod2\",container!=\"POD\"}) by (pod)",
+				expectedQuery: "sum(container_some_usage{namespace=\"somens\",pod=~\"somepod[12]\",container!=\"POD\"}) by (pod)",
 			},
 			{
 				title:          "container metrics counter",
@@ -173,7 +173,7 @@ var _ = Describe("Series Registry", func() {
 				resourceNames:  []string{"somepod1", "somepod2"},
 				metricSelector: labels.Everything(),
 
-				expectedQuery: "sum(rate(container_some_count_total{namespace=\"somens\",pod=~\"somepod1|somepod2\",container!=\"POD\"}[1m])) by (pod)",
+				expectedQuery: "sum(rate(container_some_count_total{namespace=\"somens\",pod=~\"somepod[12]\",container!=\"POD\"}[1m])) by (pod)",
 			},
 			{
 				title:          "container metrics seconds counter",
@@ -182,7 +182,7 @@ var _ = Describe("Series Registry", func() {
 				resourceNames:  []string{"somepod1", "somepod2"},
 				metricSelector: labels.Everything(),
 
-				expectedQuery: "sum(rate(container_some_time_seconds_total{namespace=\"somens\",pod=~\"somepod1|somepod2\",container!=\"POD\"}[1m])) by (pod)",
+				expectedQuery: "sum(rate(container_some_time_seconds_total{namespace=\"somens\",pod=~\"somepod[12]\",container!=\"POD\"}[1m])) by (pod)",
 			},
 			// namespaced metrics
 			{
diff --git a/pkg/naming/metrics_query.go b/pkg/naming/metrics_query.go
index e9d7069b..b6447a36 100644
--- a/pkg/naming/metrics_query.go
+++ b/pkg/naming/metrics_query.go
@@ -364,12 +364,6 @@ func compactRegexp(values []string) (string, error) {
 			return "", ErrMalformedQuery
 		}
 	}
-	if len(values) == 0 {
-		return "", nil
-	}
-	if len(values) == 1 {
-		return values[0], nil
-	}
 	expr := strings.Join(values, "|")
 	re, err := syntax.Parse(expr, syntax.POSIX)
 	if err != nil {