diff --git a/config/crd/bases/tinkerbell.org_hardware.yaml b/config/crd/bases/tinkerbell.org_hardware.yaml
index 0a535e630..c52f13bb7 100644
--- a/config/crd/bases/tinkerbell.org_hardware.yaml
+++ b/config/crd/bases/tinkerbell.org_hardware.yaml
@@ -108,6 +108,7 @@ spec:
                             format: int64
                             type: integer
                           mac:
+                            pattern: ([0-9a-f]{2}[:]){5}([0-9a-f]{2})
                             type: string
                           name_servers:
                             items:
diff --git a/pkg/apis/core/v1alpha1/hardware_types.go b/pkg/apis/core/v1alpha1/hardware_types.go
index 5b1037cb4..cdcc6e61d 100644
--- a/pkg/apis/core/v1alpha1/hardware_types.go
+++ b/pkg/apis/core/v1alpha1/hardware_types.go
@@ -115,6 +115,7 @@ type OSIE struct {
 
 // DHCP configuration.
 type DHCP struct {
+	// +kubebuilder:validation:Pattern="([0-9a-f]{2}[:]){5}([0-9a-f]{2})"
 	MAC         string   `json:"mac,omitempty"`
 	Hostname    string   `json:"hostname,omitempty"`
 	LeaseTime   int64    `json:"lease_time,omitempty"`