diff --git a/cmd/kubeadm/app/constants/constants.go b/cmd/kubeadm/app/constants/constants.go
index fee98ece17c..02b0d615c71 100644
--- a/cmd/kubeadm/app/constants/constants.go
+++ b/cmd/kubeadm/app/constants/constants.go
@@ -496,16 +496,27 @@ var (
 	// CurrentKubernetesVersion specifies current Kubernetes version supported by kubeadm
 	CurrentKubernetesVersion = getSkewedKubernetesVersion(0)
 
-	// SupportedEtcdVersion lists officially supported etcd versions with corresponding Kubernetes releases
+	// SupportedEtcdVersion lists officially supported etcd versions with corresponding
+	// Kubernetes releases.
+	//
 	// If you are updating the versions in this map, make sure to also update:
 	// - MinExternalEtcdVersion: with the minimum etcd version from this map.
-	// - DefaultEtcdVersion: with etcd version used for the current k8s release (0).
-	// The maximum length of the map should be 2, as kubeadm supports a maximum skew of -1
-	// with the control plane version.
+	// - DefaultEtcdVersion: with etcd version used for the current k8s release.
+	//
+	// The maximum length of the map should be 3. kubeadm supports a maximum skew of -1
+	// with the control plane version, but before a release the oldest k8s version in this
+	// map will be the only stable version, thus one additional version is required
+	// to be unit tested.
+	//
+	// This map should not be used directly in kubeadm code. Instead, it should be used with
+	// EtcdSupportedVersion(), as it allows for returning a valid version even if the input
+	// k8s version key is not defined (out of bounds). This allows for kubeadm to assume
+	// an etcd version even if the map is not yet updated before a release. The user will
+	// get a warning in that case, so ideally the map should be updated for each release.
 	SupportedEtcdVersion = map[uint8]string{
-		uint8(getSkewedKubernetesVersion(-2).Minor()): "3.5.24-0",
-		uint8(getSkewedKubernetesVersion(-1).Minor()): "3.6.6-0",
-		uint8(getSkewedKubernetesVersion(0).Minor()):  "3.6.6-0",
+		34: "3.6.6-0",
+		35: "3.6.6-0",
+		36: "3.6.6-0",
 	}
 
 	// KubeadmCertsClusterRoleName sets the name for the ClusterRole that allows
diff --git a/cmd/kubeadm/app/constants/constants_test.go b/cmd/kubeadm/app/constants/constants_test.go
index dea843890e1..ebd95631cff 100644
--- a/cmd/kubeadm/app/constants/constants_test.go
+++ b/cmd/kubeadm/app/constants/constants_test.go
@@ -98,10 +98,18 @@ func TestGetStaticPodFilepath(t *testing.T) {
 	}
 }
 
+func TestEtcdSupportedVersionLength(t *testing.T) {
+	const max = 3
+	if len(SupportedEtcdVersion) != max {
+		t.Fatalf("SupportedEtcdVersion must include exactly %d versions", max)
+	}
+}
+
 func TestEtcdSupportedVersion(t *testing.T) {
 	var supportedEtcdVersion = map[uint8]string{
 		17: "3.3.17-0",
-		18: "3.4.3-0",
+		18: "3.4.2-0",
+		19: "3.4.3-0",
 	}
 	var tests = []struct {
 		kubernetesVersion string
@@ -135,7 +143,7 @@ func TestEtcdSupportedVersion(t *testing.T) {
 		},
 		{
 			kubernetesVersion: "1.18.1",
-			expectedVersion:   version.MustParseSemantic("3.4.3-0"),
+			expectedVersion:   version.MustParseSemantic("3.4.2-0"),
 			expectedWarning:   false,
 			expectedError:     false,
 		},