diff --git a/metropolis/node/BUILD.bazel b/metropolis/node/BUILD.bazel
index dca6524..6ae234a 100644
--- a/metropolis/node/BUILD.bazel
+++ b/metropolis/node/BUILD.bazel
@@ -22,7 +22,6 @@
     deps = [
         "//metropolis/proto/common",
         "@com_github_vishvananda_netlink//:netlink",
-        "@io_k8s_apimachinery//pkg/util/validation",
     ],
 )
 
diff --git a/metropolis/node/labels.go b/metropolis/node/labels.go
index 93f1551..b829302 100644
--- a/metropolis/node/labels.go
+++ b/metropolis/node/labels.go
@@ -5,8 +5,6 @@
 	"regexp"
 	"strings"
 
-	"k8s.io/apimachinery/pkg/util/validation"
-
 	cpb "source.monogon.dev/metropolis/proto/common"
 )
 
@@ -43,8 +41,8 @@
 	if prefix == "" {
 		return ErrLabelEmptyPrefix
 	}
-	if errs := validation.IsDNS1123Subdomain(prefix); len(errs) > 0 {
-		return ErrLabelInvalidPrefix
+	if err := validateDomainName(prefix); err != nil {
+		return fmt.Errorf("invalid prefix: %w", err)
 	}
 	return nil
 }
diff --git a/metropolis/node/labels_test.go b/metropolis/node/labels_test.go
index c8e1a86..0457b1e 100644
--- a/metropolis/node/labels_test.go
+++ b/metropolis/node/labels_test.go
@@ -22,15 +22,21 @@
 		{"accordingtoallknownlawsofaviationthereisnowaythatabeeshouldbeabletofly", ErrLabelTooLong},
 		{"example.com/annotation", nil},
 		{"/annotation", ErrLabelEmptyPrefix},
-		{"_internal.example.com/annotation", ErrLabelInvalidPrefix},
-		{"./annotation", ErrLabelInvalidPrefix},
-		{"../annotation", ErrLabelInvalidPrefix},
-		{"tcp:80.example.com/annotation", ErrLabelInvalidPrefix},
+		{"_internal.example.com/annotation", errDomainNameInvalid},
+		{"./annotation", errDomainNameInvalid},
+		{"../annotation", errDomainNameInvalid},
+		{"tcp:80.example.com/annotation", errDomainNameInvalid},
+		{"80/annotation", errDomainNameEndsInNumber},
 		{"github.com/monogon-dev/monogon/annotation", ErrLabelInvalidPrefix},
 	} {
 		if got := ValidateLabelKey(te.in); !errors.Is(got, te.want) {
 			t.Errorf("%d (%q): wanted %v, got %v", i, te.in, te.want, got)
 		}
+		if ValidateLabelKey(te.in) == nil {
+			if errs := validation.IsQualifiedName(te.in); len(errs) != 0 {
+				t.Errorf("%d (%q): is not a valid Kubernetes qualified name: %v", i, te.in, errs)
+			}
+		}
 	}
 }