diff --git a/pkg/admission/mutator/shoot.go b/pkg/admission/mutator/shoot.go
index 2e65cbb10..219fd38e9 100644
--- a/pkg/admission/mutator/shoot.go
+++ b/pkg/admission/mutator/shoot.go
@@ -120,7 +120,10 @@ func (s *shoot) Mutate(_ context.Context, newObj, oldObj client.Object) error {
 			}
 		}
 
-		overlayConfig, _ = networkConfig["overlay"].(map[string]interface{})
+		if currentOverlayConfig, ok := networkConfig["overlay"].(map[string]interface{}); ok {
+			overlayConfig = currentOverlayConfig
+		}
+
 		if !overlayConfig["enabled"].(bool) && overlayConfig[createPodRoutesKey] == nil {
 			overlayConfig[createPodRoutesKey] = true
 			networkConfig[overlayKey] = overlayConfig
diff --git a/pkg/admission/mutator/shoot_test.go b/pkg/admission/mutator/shoot_test.go
index 2808542a0..4a86b89d3 100644
--- a/pkg/admission/mutator/shoot_test.go
+++ b/pkg/admission/mutator/shoot_test.go
@@ -171,6 +171,17 @@ var _ = Describe("Shoot mutator", func() {
 				Expect(networkConfig).To(DeepEqual(expectedConfig))
 			})
 
+			It("should disable overlay for a new shoot non empty network config", func() {
+				shoot.Spec.Networking.ProviderConfig = &runtime.RawExtension{
+					Raw: []byte(`{"foo":{"enabled":true}}`),
+				}
+				err := shootMutator.Mutate(ctx, shoot, nil)
+				Expect(err).NotTo(HaveOccurred())
+				Expect(shoot.Spec.Networking.ProviderConfig).To(Equal(&runtime.RawExtension{
+					Raw: []byte(`{"foo":{"enabled":true},"overlay":{"createPodRoutes":true,"enabled":false}}`),
+				}))
+			})
+
 			It("should take overlay field value from old shoot when unspecified in new shoot", func() {
 				oldShoot.Spec.Networking.ProviderConfig = &runtime.RawExtension{
 					Raw: []byte(`{"overlay":{"enabled":true}}`),
@@ -183,6 +194,14 @@ var _ = Describe("Shoot mutator", func() {
 			})
 		})
 
+		It("should disable overlay for a new shoot when unspecified in new and old shoot", func() {
+			err := shootMutator.Mutate(ctx, shoot, oldShoot)
+			Expect(err).NotTo(HaveOccurred())
+			Expect(shoot.Spec.Networking.ProviderConfig).To(Equal(&runtime.RawExtension{
+				Raw: []byte(`{"overlay":{"createPodRoutes":true,"enabled":false}}`),
+			}))
+		})
+
 		Context("Mutate shoot networking providerconfig for type cilium", func() {
 			BeforeEach(func() {
 				shoot.Spec.Networking.Type = pointer.String("cilium")