diff --git a/idxmgmt/ilm/config.go b/idxmgmt/ilm/config.go
index 9a3b76bd68f..adde417d2ab 100644
--- a/idxmgmt/ilm/config.go
+++ b/idxmgmt/ilm/config.go
@@ -19,6 +19,7 @@ package ilm
 
 import (
 	"fmt"
+	"strings"
 	"time"
 
 	libcommon "github.com/elastic/beats/v7/libbeat/common"
@@ -125,7 +126,7 @@ func (m *Mappings) Unpack(cfg *libcommon.Config) error {
 			mapping.Index = existing.Index
 		}
 		if mapping.IndexSuffix != "" {
-			mapping.Index = fmt.Sprintf("%s-%s", mapping.Index, mapping.IndexSuffix)
+			mapping.Index = fmt.Sprintf("%s-%s", mapping.Index, strings.ToLower(mapping.IndexSuffix))
 		}
 		(*m)[mapping.EventType] = mapping
 	}
diff --git a/idxmgmt/ilm/config_test.go b/idxmgmt/ilm/config_test.go
index f848f83466a..1732fb345bf 100644
--- a/idxmgmt/ilm/config_test.go
+++ b/idxmgmt/ilm/config_test.go
@@ -118,7 +118,7 @@ func TestConfig_Valid(t *testing.T) {
 		expected Config
 	}{
 		{name: "new policy and index suffix",
-			cfg: `{"setup":{"mapping":[{"event_type":"span","policy_name":"spanPolicy"},{"event_type":"metric","index_suffix":"production"},{"event_type":"error","index_suffix":"%{[observer.name]}"}],"policies":[{"name":"spanPolicy","policy":{"phases":{"foo":{}}}}]}}`,
+			cfg: `{"setup":{"mapping":[{"event_type":"span","policy_name":"spanPolicy"},{"event_type":"metric","index_suffix":"ProdUCtion"},{"event_type":"error","index_suffix":"%{[observer.name]}"}],"policies":[{"name":"spanPolicy","policy":{"phases":{"foo":{}}}}]}}`,
 			expected: Config{Mode: libilm.ModeAuto,
 				Setup: Setup{Enabled: true, Overwrite: false, RequirePolicy: true,
 					Mappings: map[string]Mapping{
@@ -129,7 +129,7 @@ func TestConfig_Valid(t *testing.T) {
 						"transaction": {EventType: "transaction", PolicyName: defaultPolicyName,
 							Index: "apm-9.9.9-transaction"},
 						"metric": {EventType: "metric", PolicyName: defaultPolicyName,
-							Index: "apm-9.9.9-metric-production", IndexSuffix: "production"},
+							Index: "apm-9.9.9-metric-production", IndexSuffix: "ProdUCtion"},
 						"profile": {EventType: "profile", PolicyName: defaultPolicyName,
 							Index: "apm-9.9.9-profile"},
 					},