diff --git a/pkg/api/pod/util.go b/pkg/api/pod/util.go
index 1d1a211a28e..2e425c93cd5 100644
--- a/pkg/api/pod/util.go
+++ b/pkg/api/pod/util.go
@@ -1255,6 +1255,11 @@ func hasInvalidLabelValueInAffinitySelector(spec *api.PodSpec) bool {
 }
 
 func MarkPodProposedForResize(oldPod, newPod *api.Pod) {
+	if len(newPod.Spec.Containers) != len(oldPod.Spec.Containers) {
+		// Update is invalid: ignore changes and let validation handle it
+		return
+	}
+
 	for i, c := range newPod.Spec.Containers {
 		if c.Resources.Requests == nil {
 			continue
diff --git a/pkg/api/pod/util_test.go b/pkg/api/pod/util_test.go
index c94005283a4..a99deac1a4c 100644
--- a/pkg/api/pod/util_test.go
+++ b/pkg/api/pod/util_test.go
@@ -3036,6 +3036,189 @@ func TestMarkPodProposedForResize(t *testing.T) {
 				},
 			},
 		},
+		{
+			desc: "the number of containers in the pod has increased; no action should be taken.",
+			newPod: &api.Pod{
+				Spec: api.PodSpec{
+					Containers: []api.Container{
+						{
+							Name:  "c1",
+							Image: "image",
+							Resources: api.ResourceRequirements{
+								Requests: api.ResourceList{api.ResourceCPU: resource.MustParse("100m")},
+								Limits:   api.ResourceList{api.ResourceCPU: resource.MustParse("200m")},
+							},
+						},
+						{
+							Name:  "c2",
+							Image: "image",
+							Resources: api.ResourceRequirements{
+								Requests: api.ResourceList{api.ResourceCPU: resource.MustParse("300m")},
+								Limits:   api.ResourceList{api.ResourceCPU: resource.MustParse("400m")},
+							},
+						},
+					},
+				},
+				Status: api.PodStatus{
+					ContainerStatuses: []api.ContainerStatus{
+						{
+							Name:               "c1",
+							Image:              "image",
+							AllocatedResources: api.ResourceList{api.ResourceCPU: resource.MustParse("100m")},
+						},
+						{
+							Name:               "c2",
+							Image:              "image",
+							AllocatedResources: api.ResourceList{api.ResourceCPU: resource.MustParse("200m")},
+						},
+					},
+				},
+			},
+			oldPod: &api.Pod{
+				Spec: api.PodSpec{
+					Containers: []api.Container{
+						{
+							Name:  "c1",
+							Image: "image",
+							Resources: api.ResourceRequirements{
+								Requests: api.ResourceList{api.ResourceCPU: resource.MustParse("100m")},
+								Limits:   api.ResourceList{api.ResourceCPU: resource.MustParse("200m")},
+							},
+						},
+					},
+				},
+				Status: api.PodStatus{
+					ContainerStatuses: []api.ContainerStatus{
+						{
+							Name:               "c1",
+							Image:              "image",
+							AllocatedResources: api.ResourceList{api.ResourceCPU: resource.MustParse("100m")},
+						},
+					},
+				},
+			},
+			expectedPod: &api.Pod{
+				Spec: api.PodSpec{
+					Containers: []api.Container{
+						{
+							Name:  "c1",
+							Image: "image",
+							Resources: api.ResourceRequirements{
+								Requests: api.ResourceList{api.ResourceCPU: resource.MustParse("100m")},
+								Limits:   api.ResourceList{api.ResourceCPU: resource.MustParse("200m")},
+							},
+						},
+						{
+							Name:  "c2",
+							Image: "image",
+							Resources: api.ResourceRequirements{
+								Requests: api.ResourceList{api.ResourceCPU: resource.MustParse("300m")},
+								Limits:   api.ResourceList{api.ResourceCPU: resource.MustParse("400m")},
+							},
+						},
+					},
+				},
+				Status: api.PodStatus{
+					ContainerStatuses: []api.ContainerStatus{
+						{
+							Name:               "c1",
+							Image:              "image",
+							AllocatedResources: api.ResourceList{api.ResourceCPU: resource.MustParse("100m")},
+						},
+						{
+							Name:               "c2",
+							Image:              "image",
+							AllocatedResources: api.ResourceList{api.ResourceCPU: resource.MustParse("200m")},
+						},
+					},
+				},
+			},
+		},
+		{
+			desc: "the number of containers in the pod has decreased; no action should be taken.",
+			newPod: &api.Pod{
+				Spec: api.PodSpec{
+					Containers: []api.Container{
+						{
+							Name:  "c1",
+							Image: "image",
+							Resources: api.ResourceRequirements{
+								Requests: api.ResourceList{api.ResourceCPU: resource.MustParse("100m")},
+								Limits:   api.ResourceList{api.ResourceCPU: resource.MustParse("200m")},
+							},
+						},
+					},
+				},
+				Status: api.PodStatus{
+					ContainerStatuses: []api.ContainerStatus{
+						{
+							Name:               "c1",
+							Image:              "image",
+							AllocatedResources: api.ResourceList{api.ResourceCPU: resource.MustParse("100m")},
+						},
+					},
+				},
+			},
+			oldPod: &api.Pod{
+				Spec: api.PodSpec{
+					Containers: []api.Container{
+						{
+							Name:  "c1",
+							Image: "image",
+							Resources: api.ResourceRequirements{
+								Requests: api.ResourceList{api.ResourceCPU: resource.MustParse("100m")},
+								Limits:   api.ResourceList{api.ResourceCPU: resource.MustParse("200m")},
+							},
+						},
+						{
+							Name:  "c2",
+							Image: "image",
+							Resources: api.ResourceRequirements{
+								Requests: api.ResourceList{api.ResourceCPU: resource.MustParse("200m")},
+								Limits:   api.ResourceList{api.ResourceCPU: resource.MustParse("300m")},
+							},
+						},
+					},
+				},
+				Status: api.PodStatus{
+					ContainerStatuses: []api.ContainerStatus{
+						{
+							Name:               "c1",
+							Image:              "image",
+							AllocatedResources: api.ResourceList{api.ResourceCPU: resource.MustParse("100m")},
+						},
+						{
+							Name:               "c2",
+							Image:              "image",
+							AllocatedResources: api.ResourceList{api.ResourceCPU: resource.MustParse("200m")},
+						},
+					},
+				},
+			},
+			expectedPod: &api.Pod{
+				Spec: api.PodSpec{
+					Containers: []api.Container{
+						{
+							Name:  "c1",
+							Image: "image",
+							Resources: api.ResourceRequirements{
+								Requests: api.ResourceList{api.ResourceCPU: resource.MustParse("100m")},
+								Limits:   api.ResourceList{api.ResourceCPU: resource.MustParse("200m")},
+							},
+						},
+					},
+				},
+				Status: api.PodStatus{
+					ContainerStatuses: []api.ContainerStatus{
+						{
+							Name:               "c1",
+							Image:              "image",
+							AllocatedResources: api.ResourceList{api.ResourceCPU: resource.MustParse("100m")},
+						},
+					},
+				},
+			},
+		},
 	}
 	for _, tc := range testCases {
 		t.Run(tc.desc, func(t *testing.T) {