diff --git a/internal/kubernetes/watcher/error.go b/internal/kubernetes/watcher/error.go
new file mode 100644
index 000000000..3ecb3a6d3
--- /dev/null
+++ b/internal/kubernetes/watcher/error.go
@@ -0,0 +1,65 @@
+package watcher
+
+import (
+	"fmt"
+	"strings"
+)
+
+type ErrorNotFound struct {
+	Cluster   string
+	Namespace string
+	Name      string
+}
+
+func (e *ErrorNotFound) Error() string {
+	return "not found: " + e.Cluster + "/" + e.Namespace + "/" + e.Name
+}
+
+func (e *ErrorNotFound) GraphError() string {
+	return "Resource not found: " + e.Cluster + "/" + e.Namespace + "/" + e.Name
+}
+
+func (e *ErrorNotFound) As(v any) bool {
+	if _, ok := v.(*ErrorNotFound); ok {
+		return true
+	}
+
+	return false
+}
+
+func (e *ErrorNotFound) Is(v error) bool {
+	if _, ok := v.(*ErrorNotFound); ok {
+		return true
+	}
+
+	return false
+}
+
+type ErrorUnknownEnvironment struct {
+	Environment string
+	Valid       []string
+}
+
+func (e *ErrorUnknownEnvironment) Error() string {
+	return "unknown environment: " + e.Environment
+}
+
+func (e *ErrorUnknownEnvironment) GraphError() string {
+	return fmt.Sprintf("Unknown environment %q. Valid values are [%s]", e.Environment, strings.Join(e.Valid, ", "))
+}
+
+func (e *ErrorUnknownEnvironment) As(v any) bool {
+	if _, ok := v.(*ErrorUnknownEnvironment); ok {
+		return true
+	}
+
+	return false
+}
+
+func (e *ErrorUnknownEnvironment) Is(v error) bool {
+	if _, ok := v.(*ErrorUnknownEnvironment); ok {
+		return true
+	}
+
+	return false
+}
diff --git a/internal/kubernetes/watcher/filter.go b/internal/kubernetes/watcher/filter.go
index 3c0b008af..d36484544 100644
--- a/internal/kubernetes/watcher/filter.go
+++ b/internal/kubernetes/watcher/filter.go
@@ -1,36 +1,8 @@
 package watcher
 
-import "k8s.io/apimachinery/pkg/labels"
-
-type ErrorNotFound struct {
-	Cluster   string
-	Namespace string
-	Name      string
-}
-
-func (e *ErrorNotFound) Error() string {
-	return "not found: " + e.Cluster + "/" + e.Namespace + "/" + e.Name
-}
-
-func (e *ErrorNotFound) GraphError() string {
-	return "Resource not found: " + e.Cluster + "/" + e.Namespace + "/" + e.Name
-}
-
-func (e *ErrorNotFound) As(v any) bool {
-	if _, ok := v.(*ErrorNotFound); ok {
-		return true
-	}
-
-	return false
-}
-
-func (e *ErrorNotFound) Is(v error) bool {
-	if _, ok := v.(*ErrorNotFound); ok {
-		return true
-	}
-
-	return false
-}
+import (
+	"k8s.io/apimachinery/pkg/labels"
+)
 
 type EnvironmentWrapper[T Object] struct {
 	Cluster string
diff --git a/internal/kubernetes/watcher/watcher.go b/internal/kubernetes/watcher/watcher.go
index 2f1bd0dd0..32dfeca45 100644
--- a/internal/kubernetes/watcher/watcher.go
+++ b/internal/kubernetes/watcher/watcher.go
@@ -2,7 +2,6 @@ package watcher
 
 import (
 	"context"
-	"fmt"
 	"slices"
 	"strings"
 
@@ -54,13 +53,14 @@ type watcherSettings struct {
 type WatcherHook[T Object] func(cluster string, obj T)
 
 type Watcher[T Object] struct {
-	watchers        []*clusterWatcher[T]
-	log             logrus.FieldLogger
-	resourceCounter metric.Int64UpDownCounter
-	watchedType     string
-	onAdd           WatcherHook[T]
-	onUpdate        WatcherHook[T]
-	onRemove        WatcherHook[T]
+	watchers         []*clusterWatcher[T]
+	environmentNames []string
+	log              logrus.FieldLogger
+	resourceCounter  metric.Int64UpDownCounter
+	watchedType      string
+	onAdd            WatcherHook[T]
+	onUpdate         WatcherHook[T]
+	onRemove         WatcherHook[T]
 }
 
 func newWatcher[T Object](mgr *Manager, obj T, settings *watcherSettings, log logrus.FieldLogger) *Watcher[T] {
@@ -69,15 +69,16 @@ func newWatcher[T Object](mgr *Manager, obj T, settings *watcherSettings, log lo
 		resourceCounter: mgr.resourceCounter,
 	}
 	for cluster, client := range mgr.managers {
-		cluster = environmentmapper.EnvironmentName(cluster)
-		watcher, gvr := newClusterWatcher(client, cluster, w, obj, settings, log.WithField("cluster", cluster))
+		environmentName := environmentmapper.EnvironmentName(cluster)
+		watcher, gvr := newClusterWatcher(client, environmentName, w, obj, settings, log.WithField("cluster", environmentName))
 		if !watcher.isRegistered {
 			continue
 		}
 		w.watchedType = gvr.String()
 
 		w.watchers = append(w.watchers, watcher)
-		mgr.addCacheSync(cluster, gvr.String(), watcher.informer.Informer().HasSynced)
+		w.environmentNames = append(w.environmentNames, environmentName)
+		mgr.addCacheSync(environmentName, gvr.String(), watcher.informer.Informer().HasSynced)
 	}
 	return w
 }
@@ -297,7 +298,7 @@ func (w *Watcher[T]) ImpersonatedClient(ctx context.Context, cluster string, opt
 		}
 	}
 
-	return nil, fmt.Errorf("no watcher for cluster %s", cluster)
+	return nil, w.unknownEnvironmentError(cluster)
 }
 
 func (w *Watcher[T]) ImpersonatedClientWithNamespace(ctx context.Context, cluster, namespace string, opts ...ImpersonatedClientOption) (dynamic.ResourceInterface, error) {
@@ -316,7 +317,11 @@ func (w *Watcher[T]) SystemAuthenticatedClient(ctx context.Context, cluster stri
 		}
 	}
 
-	return nil, fmt.Errorf("no watcher for cluster %s", cluster)
+	return nil, w.unknownEnvironmentError(cluster)
+}
+
+func (w *Watcher[T]) unknownEnvironmentError(cluster string) error {
+	return &ErrorUnknownEnvironment{Environment: cluster, Valid: w.environmentNames}
 }
 
 func (w *Watcher[T]) OnRemove(fn WatcherHook[T]) {
diff --git a/internal/persistence/aivencredentials/queries.go b/internal/persistence/aivencredentials/queries.go
index f4c858490..8729aec1d 100644
--- a/internal/persistence/aivencredentials/queries.go
+++ b/internal/persistence/aivencredentials/queries.go
@@ -5,6 +5,8 @@ import (
 	"crypto/sha256"
 	"encoding/base64"
 	"fmt"
+	"maps"
+	"slices"
 	"strconv"
 	"strings"
 	"time"
@@ -100,7 +102,8 @@ func getClient(ctx context.Context, environmentName string) (dynamic.Interface,
 	clusterName := environmentmapper.ClusterName(environmentName)
 	client, ok := l.dynamicClients[clusterName]
 	if !ok {
-		return nil, fmt.Errorf("unknown environment: %s", environmentName)
+		valid := strings.Join(slices.Collect(maps.Keys(l.dynamicClients)), ", ")
+		return nil, apierror.Errorf("Unknown environment %q. Valid values are [%s]", environmentName, valid)
 	}
 	return client, nil
 }