diff --git a/pkg/reconciler/labeler/accessors.go b/pkg/reconciler/labeler/accessors.go
index bd30b793e87c..688ababcda87 100644
--- a/pkg/reconciler/labeler/accessors.go
+++ b/pkg/reconciler/labeler/accessors.go
@@ -18,6 +18,7 @@ package labeler
 
 import (
 	"context"
+	"sort"
 	"strings"
 
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
@@ -128,7 +129,9 @@ func updateRouteAnnotation(acc kmeta.Accessor, routeName string, diffAnn map[str
 			return
 		}
 		valSet.Delete(routeName)
-		diffAnn[serving.RoutesAnnotationKey] = strings.Join(valSet.UnsortedList(), ",")
+		sorted := valSet.UnsortedList()
+		sort.Strings(sorted)
+		diffAnn[serving.RoutesAnnotationKey] = strings.Join(sorted, ",")
 
 	case !has && !remove:
 		if len(valSet) == 0 {
@@ -136,7 +139,9 @@ func updateRouteAnnotation(acc kmeta.Accessor, routeName string, diffAnn map[str
 			return
 		}
 		valSet.Insert(routeName)
-		diffAnn[serving.RoutesAnnotationKey] = strings.Join(valSet.UnsortedList(), ",")
+		sorted := valSet.UnsortedList()
+		sort.Strings(sorted)
+		diffAnn[serving.RoutesAnnotationKey] = strings.Join(sorted, ",")
 	}
 }
 
diff --git a/pkg/reconciler/service/resources/configuration.go b/pkg/reconciler/service/resources/configuration.go
index 241ac7f11d54..f04662cb9b6a 100644
--- a/pkg/reconciler/service/resources/configuration.go
+++ b/pkg/reconciler/service/resources/configuration.go
@@ -17,6 +17,7 @@ limitations under the License.
 package resources
 
 import (
+	"sort"
 	"strings"
 
 	corev1 "k8s.io/api/core/v1"
@@ -48,7 +49,9 @@ func MakeConfigurationFromExisting(service *v1.Service, existing *v1.Configurati
 	routeName := names.Route(service)
 	set := labeler.GetListAnnValue(existing.Annotations, serving.RoutesAnnotationKey)
 	set.Insert(routeName)
-	anns[serving.RoutesAnnotationKey] = strings.Join(set.UnsortedList(), ",")
+	sorted := set.UnsortedList()
+	sort.Strings(sorted)
+	anns[serving.RoutesAnnotationKey] = strings.Join(sorted, ",")
 
 	return &v1.Configuration{
 		ObjectMeta: metav1.ObjectMeta{