diff --git a/pkg/alertmanager/api.go b/pkg/alertmanager/api.go
index daf517feec0..793adbcbba7 100644
--- a/pkg/alertmanager/api.go
+++ b/pkg/alertmanager/api.go
@@ -147,7 +147,7 @@ func (am *MultitenantAlertmanager) SetUserConfig(w http.ResponseWriter, r *http.
 	}
 
 	cfgDesc := alertspb.ToProto(cfg.AlertmanagerConfig, cfg.TemplateFiles, userID)
-	if err := validateUserConfig(logger, cfgDesc, am.limits, userID); err != nil {
+	if err := validateUserConfig(logger, cfgDesc, am.limits, userID, am.cfg.UTF8StrictMode); err != nil {
 		level.Warn(logger).Log("msg", errValidatingConfig, "err", err.Error())
 		http.Error(w, fmt.Sprintf("%s: %s", errValidatingConfig, err.Error()), http.StatusBadRequest)
 		return
@@ -185,8 +185,10 @@ func (am *MultitenantAlertmanager) DeleteUserConfig(w http.ResponseWriter, r *ht
 }
 
 // Partially copied from: https://github.com/prometheus/alertmanager/blob/8e861c646bf67599a1704fc843c6a94d519ce312/cli/check_config.go#L65-L96
-func validateUserConfig(logger log.Logger, cfg alertspb.AlertConfigDesc, limits Limits, user string) error {
-	validateMatchersInConfigDesc(logger, "api", cfg)
+func validateUserConfig(logger log.Logger, cfg alertspb.AlertConfigDesc, limits Limits, user string, utf8StrictMode bool) error {
+	if !utf8StrictMode {
+		validateMatchersInConfigDesc(logger, "api", cfg)
+	}
 
 	// We don't have a valid use case for empty configurations. If a tenant does not have a
 	// configuration set and issue a request to the Alertmanager, we'll a) upload an empty
diff --git a/pkg/alertmanager/api_test.go b/pkg/alertmanager/api_test.go
index f4cdefcce30..6948161bfb6 100644
--- a/pkg/alertmanager/api_test.go
+++ b/pkg/alertmanager/api_test.go
@@ -881,6 +881,7 @@ alertmanager_config: |
 
 	limits := &mockAlertManagerLimits{}
 	am := &MultitenantAlertmanager{
+		cfg:    &MultitenantAlertmanagerConfig{},
 		store:  prepareInMemoryAlertStore(),
 		logger: test.NewTestingLogger(t),
 		limits: limits,
diff --git a/pkg/alertmanager/multitenant.go b/pkg/alertmanager/multitenant.go
index ab79594e425..b63b244f613 100644
--- a/pkg/alertmanager/multitenant.go
+++ b/pkg/alertmanager/multitenant.go
@@ -806,12 +806,14 @@ type amConfig struct {
 // setConfig applies the given configuration to the alertmanager for `userID`,
 // creating an alertmanager if it doesn't already exist.
 func (am *MultitenantAlertmanager) setConfig(cfg amConfig) error {
-	// Instead of using "config" as the origin, as in Prometheus Alertmanager, we use "tenant".
-	// The reason for this that the config.Load function uses the origin "config",
-	// which is correct, but Mimir uses config.Load to validate both API requests and tenant
-	// configurations. This means metrics from API requests are confused with metrics from
-	// tenant configurations. To avoid this confusion, we use a different origin.
-	validateMatchersInConfigDesc(am.logger, "tenant", cfg.AlertConfigDesc)
+	if !am.cfg.UTF8StrictMode {
+		// Instead of using "config" as the origin, as in Prometheus Alertmanager, we use "tenant".
+		// The reason for this that the config.Load function uses the origin "config",
+		// which is correct, but Mimir uses config.Load to validate both API requests and tenant
+		// configurations. This means metrics from API requests are confused with metrics from
+		// tenant configurations. To avoid this confusion, we use a different origin.
+		validateMatchersInConfigDesc(am.logger, "tenant", cfg.AlertConfigDesc)
+	}
 
 	level.Debug(am.logger).Log("msg", "setting config", "user", cfg.User)