diff --git a/pkg/reconciler/topology/partitionset/partitioning_test.go b/pkg/reconciler/topology/partitionset/partitioning_test.go
index 6f0335e7630..40231603302 100644
--- a/pkg/reconciler/topology/partitionset/partitioning_test.go
+++ b/pkg/reconciler/topology/partitionset/partitioning_test.go
@@ -135,6 +135,12 @@ func TestPartition(t *testing.T) {
 	for _, v := range matchLabelsMap {
 		require.Equal(t, "prod", v["environment"], "Expected that all partitions have a label selector for environment = prod")
 	}
+
+	matchLabelsMap = partition(shards, []string{"region", "environment"}, map[string]string{"environment": "prod"})
+	require.Equal(t, map[string]map[string]string{
+		"+environment=prod+region=Asia":   {"environment": "prod", "region": "Asia"},
+		"+environment=prod+region=Europe": {"environment": "prod", "region": "Europe"},
+	}, matchLabelsMap, "Labels being both a dimension and in the shard selector should only be considered once")
 }
 
 func TestGeneratePartitionName(t *testing.T) {
diff --git a/pkg/reconciler/topology/partitionset/partitionset_controller_test.go b/pkg/reconciler/topology/partitionset/partitionset_controller_test.go
index 2efb014228c..ff65e748198 100644
--- a/pkg/reconciler/topology/partitionset/partitionset_controller_test.go
+++ b/pkg/reconciler/topology/partitionset/partitionset_controller_test.go
@@ -92,6 +92,13 @@ func TestReconcile(t *testing.T) {
 			wantPartitionCount:    2,
 			wantCountCreated:      2,
 		},
+		"Existing partition kept with selector and dimension overlapping": {
+			withMatchLabelOverlap:  true,
+			existingValidPartition: true,
+			wantPartitionsReady:    true,
+			wantPartitionCount:     2,
+			wantCountCreated:       1,
+		},
 	}
 
 	for name, tc := range tests {
diff --git a/pkg/reconciler/topology/partitionset/partitionset_reconcile.go b/pkg/reconciler/topology/partitionset/partitionset_reconcile.go
index 1e9b89c5326..3dd1fd52e72 100644
--- a/pkg/reconciler/topology/partitionset/partitionset_reconcile.go
+++ b/pkg/reconciler/topology/partitionset/partitionset_reconcile.go
@@ -196,12 +196,11 @@ func (c *controller) reconcile(ctx context.Context, partitionSet *topologyv1alph
 // so that Partitions not referring to any Shard would not get created.
 func partition(shards []*corev1alpha1.Shard, dimensions []string, shardSelectorLabels map[string]string) (matchLabelsMap map[string]map[string]string) {
 	matchLabelsMap = make(map[string]map[string]string)
-	l := make([]string, len(dimensions), len(dimensions)+len(shardSelectorLabels))
-	copy(l, dimensions)
-	for label := range shardSelectorLabels {
-		l = append(l, label)
-	}
-	sort.Strings(l) // Sorting for consistent comparison.
+	// A label can be both a dimension and part of the shard selector matchLabels.
+	// It must only be considered once, otherwise the generated key would not
+	// match the one computed from the matchLabels of existing Partitions.
+	// sets.List returns the labels sorted for consistent comparison.
+	l := sets.List(sets.KeySet(shardSelectorLabels).Insert(dimensions...))
 	for _, shard := range shards {
 		key := ""
 		selector := make(map[string]string)