diff --git a/pkg/kubectl/cmd/diff/diff.go b/pkg/kubectl/cmd/diff/diff.go
index 797a9fde1ff..076439d2647 100644
--- a/pkg/kubectl/cmd/diff/diff.go
+++ b/pkg/kubectl/cmd/diff/diff.go
@@ -49,7 +49,7 @@ var (
 
 		Output is always YAML.
 
-		KUBERNETES_EXTERNAL_DIFF environment variable can be used to select your own
+		KUBECTL_EXTERNAL_DIFF environment variable can be used to select your own
 		diff command. By default, the "diff" command available in your path will be
 		run with "-u" (unicode) and "-N" (treat new files as empty) options.`))
 	diffExample = templates.Examples(i18n.T(`
@@ -97,7 +97,7 @@ func NewCmdDiff(f cmdutil.Factory, streams genericclioptions.IOStreams) *cobra.C
 }
 
 // DiffProgram finds and run the diff program. The value of
-// KUBERNETES_EXTERNAL_DIFF environment variable will be used a diff
+// KUBECTL_EXTERNAL_DIFF environment variable will be used a diff
 // program. By default, `diff(1)` will be used.
 type DiffProgram struct {
 	Exec exec.Interface
@@ -106,7 +106,7 @@ type DiffProgram struct {
 
 func (d *DiffProgram) getCommand(args ...string) exec.Cmd {
 	diff := ""
-	if envDiff := os.Getenv("KUBERNETES_EXTERNAL_DIFF"); envDiff != "" {
+	if envDiff := os.Getenv("KUBECTL_EXTERNAL_DIFF"); envDiff != "" {
 		diff = envDiff
 	} else {
 		diff = "diff"
@@ -122,8 +122,7 @@ func (d *DiffProgram) getCommand(args ...string) exec.Cmd {
 
 // Run runs the detected diff program. `from` and `to` are the directory to diff.
 func (d *DiffProgram) Run(from, to string) error {
-	d.getCommand(from, to).Run() // Ignore diff return code
-	return nil
+	return d.getCommand(from, to).Run()
 }
 
 // Printer is used to print an object.
@@ -397,8 +396,5 @@ func RunDiff(f cmdutil.Factory, diff *DiffProgram, options *DiffOptions) error {
 		return err
 	}
 
-	// Error ignore on purpose. diff(1) for example, returns an error if there is any diff.
-	_ = differ.Run(diff)
-
-	return nil
+	return differ.Run(diff)
 }
diff --git a/pkg/kubectl/cmd/diff/diff_test.go b/pkg/kubectl/cmd/diff/diff_test.go
index 9a88512ee58..2b833e551db 100644
--- a/pkg/kubectl/cmd/diff/diff_test.go
+++ b/pkg/kubectl/cmd/diff/diff_test.go
@@ -52,7 +52,7 @@ func (f *FakeObject) Live() runtime.Object {
 }
 
 func TestDiffProgram(t *testing.T) {
-	os.Setenv("KUBERNETES_EXTERNAL_DIFF", "echo")
+	os.Setenv("KUBECTL_EXTERNAL_DIFF", "echo")
 	streams, _, stdout, _ := genericclioptions.NewTestIOStreams()
 	diff := DiffProgram{
 		IOStreams: streams,
diff --git a/test/cmd/diff.sh b/test/cmd/diff.sh
index d52a75bdfce..bc763473773 100755
--- a/test/cmd/diff.sh
+++ b/test/cmd/diff.sh
@@ -27,12 +27,12 @@ run_kubectl_diff_tests() {
     kube::log::status "Testing kubectl diff"
 
     # Test that it works when the live object doesn't exist
-    output_message=$(kubectl diff -f hack/testdata/pod.yaml)
+    output_message=$(! kubectl diff -f hack/testdata/pod.yaml)
     kube::test::if_has_string "${output_message}" 'test-pod'
 
     kubectl apply -f hack/testdata/pod.yaml
 
-    output_message=$(kubectl diff -f hack/testdata/pod-changed.yaml)
+    output_message=$(! kubectl diff -f hack/testdata/pod-changed.yaml)
     kube::test::if_has_string "${output_message}" 'k8s.gcr.io/pause:3.0'
 
     kubectl delete -f  hack/testdata/pod.yaml