diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3e2a7ffd41..68d4985ad8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -33,6 +33,7 @@ We use *breaking :warning:* to mark changes that are not backward compatible (re
 - [#4340](https://github.com/thanos-io/thanos/pull/4340) UI: now displays the duration and all annotations of an alert in the alerts page.
 - [#4348](https://github.com/thanos-io/thanos/pull/4348) Fixed parsing of the port in the log middleware.
 - [#4417](https://github.com/thanos-io/thanos/pull/4417) UI: fixed the night mode in Bucket UI.
+- [#4442](https://github.com/thanos-io/thanos/pull/4442) Ruler: fix SIGHUP reload signal not working.
 
 ### Changed
 
diff --git a/cmd/thanos/rule.go b/cmd/thanos/rule.go
index ff5ca1310c..1872e6e935 100644
--- a/cmd/thanos/rule.go
+++ b/cmd/thanos/rule.go
@@ -80,7 +80,6 @@ type ruleConfig struct {
 	ruleFiles      []string
 	objStoreConfig *extflag.PathOrContent
 	dataDir        string
-	reloadSignal   <-chan struct{}
 	lset           labels.Labels
 }
 
@@ -195,6 +194,7 @@ func registerRule(app *extkingpin.App) {
 			tracer,
 			comp,
 			*conf,
+			reload,
 			getFlagsMap(cmd.Flags()),
 			httpLogOpts,
 			grpcLogOpts,
@@ -257,6 +257,7 @@ func runRule(
 	tracer opentracing.Tracer,
 	comp component.Component,
 	conf ruleConfig,
+	reloadSignal <-chan struct{},
 	flagsMap map[string]string,
 	httpLogOpts []logging.Option,
 	grpcLogOpts []grpc_logging.Option,
@@ -483,7 +484,7 @@ func runRule(
 			}
 			for {
 				select {
-				case <-conf.reloadSignal:
+				case <-reloadSignal:
 					if err := reloadRules(logger, conf.ruleFiles, ruleMgr, conf.evalInterval, metrics); err != nil {
 						level.Error(logger).Log("msg", "reload rules by sighup failed", "err", err)
 					}
diff --git a/test/e2e/rule_test.go b/test/e2e/rule_test.go
index e2ee815132..3e7f6a2069 100644
--- a/test/e2e/rule_test.go
+++ b/test/e2e/rule_test.go
@@ -71,9 +71,39 @@ groups:
       severity: page
     annotations:
       summary: "I always complain and I have been loaded via /-/reload."
+`
+	testAlertRuleAddedLaterSignal = `
+groups:
+- name: example
+  interval: 1s
+  partial_response_strategy: "WARN"
+  rules:
+  - alert: TestAlert_HasBeenLoadedViaWebHandler
+    # It must be based on actual metric, otherwise call to StoreAPI would be not involved.
+    expr: absent(some_metric)
+    labels:
+      severity: page
+    annotations:
+      summary: "I always complain and I have been loaded via sighup signal."
+- name: example2
+  interval: 1s
+  partial_response_strategy: "WARN"
+  rules:
+  - alert: TestAlert_HasBeenLoadedViaWebHandler
+    # It must be based on actual metric, otherwise call to StoreAPI would be not involved.
+    expr: absent(some_metric)
+    labels:
+      severity: page
+    annotations:
+      summary: "I always complain and I have been loaded via sighup signal."
 `
 )
 
+type rulesResp struct {
+	Status string
+	Data   *rulespb.RuleGroups
+}
+
 func createRuleFile(t *testing.T, path, content string) {
 	t.Helper()
 	err := ioutil.WriteFile(path, []byte(content), 0666)
@@ -97,6 +127,30 @@ func reloadRulesHTTP(t *testing.T, ctx context.Context, endpoint string) {
 	testutil.Equals(t, 200, resp.StatusCode)
 }
 
+func reloadRulesSignal(t *testing.T, r *e2ethanos.Service) {
+	c := e2e.NewCommand("kill", "-1", "1")
+	_, _, err := r.Exec(c)
+	testutil.Ok(t, err)
+}
+
+func checkReloadSuccessful(t *testing.T, ctx context.Context, endpoint string, expectedRulegroupCount int) {
+	req, err := http.NewRequestWithContext(ctx, "GET", "http://"+endpoint+"/api/v1/rules", ioutil.NopCloser(bytes.NewReader(nil)))
+	testutil.Ok(t, err)
+	resp, err := http.DefaultClient.Do(req)
+	testutil.Ok(t, err)
+	testutil.Equals(t, 200, resp.StatusCode)
+
+	body, _ := ioutil.ReadAll(resp.Body)
+	testutil.Ok(t, resp.Body.Close())
+
+	var data = rulesResp{}
+
+	testutil.Ok(t, json.Unmarshal(body, &data))
+	testutil.Equals(t, "success", data.Status)
+
+	testutil.Assert(t, len(data.Data.Groups) == expectedRulegroupCount, fmt.Sprintf("expected there to be %d rule groups", expectedRulegroupCount))
+}
+
 func rulegroupCorrectData(t *testing.T, ctx context.Context, endpoint string) {
 	req, err := http.NewRequestWithContext(ctx, "GET", "http://"+endpoint+"/api/v1/rules", ioutil.NopCloser(bytes.NewReader(nil)))
 	testutil.Ok(t, err)
@@ -108,10 +162,7 @@ func rulegroupCorrectData(t *testing.T, ctx context.Context, endpoint string) {
 	body, err := ioutil.ReadAll(resp.Body)
 	testutil.Ok(t, err)
 
-	var data struct {
-		Status string
-		Data   *rulespb.RuleGroups
-	}
+	var data = rulesResp{}
 
 	testutil.Ok(t, json.Unmarshal(body, &data))
 	testutil.Equals(t, "success", data.Status)
@@ -317,12 +368,18 @@ func TestRule(t *testing.T) {
 		rulegroupCorrectData(t, ctx, r.HTTPEndpoint())
 	})
 
-	t.Run("reload works", func(t *testing.T) {
-		// Add a new rule via /-/reload.
-		// TODO(GiedriusS): add a test for reloading via SIGHUP. Need to extend e2e framework to expose PIDs.
+	t.Run("signal reload works", func(t *testing.T) {
+		// Add a new rule via sending sighup
+		createRuleFile(t, fmt.Sprintf("%s/newrule.yaml", rulesPath), testAlertRuleAddedLaterSignal)
+		reloadRulesSignal(t, r)
+		checkReloadSuccessful(t, ctx, r.HTTPEndpoint(), 4)
+	})
 
+	t.Run("http reload works", func(t *testing.T) {
+		// Add a new rule via /-/reload.
 		createRuleFile(t, fmt.Sprintf("%s/newrule.yaml", rulesPath), testAlertRuleAddedLaterWebHandler)
 		reloadRulesHTTP(t, ctx, r.HTTPEndpoint())
+		checkReloadSuccessful(t, ctx, r.HTTPEndpoint(), 3)
 	})
 
 	queryAndAssertSeries(t, ctx, q.HTTPEndpoint(), "ALERTS", promclient.QueryOptions{