diff --git a/api/v1/externalservice_types.go b/api/v1/externalservice_types.go
index afb58ed..db35bc6 100644
--- a/api/v1/externalservice_types.go
+++ b/api/v1/externalservice_types.go
@@ -16,7 +16,6 @@ limitations under the License.
 package v1
 
 import (
-	"github.com/golang/protobuf/ptypes/duration"
 	v1 "k8s.io/api/core/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 )
@@ -67,10 +66,10 @@ type ExternalServiceSpec struct {
 	// Input to the --log-level command line option. See the help text for the available log levels and the default.
 	EnvoyLogLevel string `json:"envoyArguments,omitempty"`
 
-	// Corresponds to Envoy's dns_refresh_rate config field for this cluster.
+	// Corresponds to Envoy's dns_refresh_rate config field for this cluster, in seconds
 	// See	https://www.envoyproxy.io/docs/envoy/latest/api-v3/config/cluster/v3/cluster.proto
 	// +optional
-	EnvoyDnsRefreshRate *duration.Duration `json:"envoy_dns_refresh_rate,omitempty"`
+	EnvoyDnsRefreshRateS int64 `json:"envoy_dns_refresh_rate,omitempty"`
 
 	// Corresponds to Envoy's respect_dns_ttl config field for this cluster.
 	// See	https://www.envoyproxy.io/docs/envoy/latest/api-v3/config/cluster/v3/cluster.proto
diff --git a/api/v1/zz_generated.deepcopy.go b/api/v1/zz_generated.deepcopy.go
index 3c597f3..9e690a8 100644
--- a/api/v1/zz_generated.deepcopy.go
+++ b/api/v1/zz_generated.deepcopy.go
@@ -1,5 +1,4 @@
 //go:build !ignore_autogenerated
-// +build !ignore_autogenerated
 
 /*
 
@@ -21,6 +20,7 @@ limitations under the License.
 package v1
 
 import (
+	durationpb "google.golang.org/protobuf/types/known/durationpb"
 	corev1 "k8s.io/api/core/v1"
 	runtime "k8s.io/apimachinery/pkg/runtime"
 )
@@ -144,6 +144,11 @@ func (in *ExternalServiceSpec) DeepCopyInto(out *ExternalServiceSpec) {
 		*out = new(uint32)
 		**out = **in
 	}
+	if in.EnvoyDnsRefreshRate != nil {
+		in, out := &in.EnvoyDnsRefreshRate, &out.EnvoyDnsRefreshRate
+		*out = new(durationpb.Duration)
+		(*in).DeepCopyInto(*out)
+	}
 }
 
 // DeepCopy is an autogenerated deepcopy function, copying the receiver, creating a new ExternalServiceSpec.
diff --git a/config/crd/bases/egress.monzo.com_externalservices.yaml b/config/crd/bases/egress.monzo.com_externalservices.yaml
index 3d614b1..d6300c7 100644
--- a/config/crd/bases/egress.monzo.com_externalservices.yaml
+++ b/config/crd/bases/egress.monzo.com_externalservices.yaml
@@ -42,11 +42,11 @@ spec:
               envoyLogLevel:
                 description:  Input to the --log-level command line option. See the help text for the available log levels and the default.
                 type: string
-              envoyDnsRefreshRate:
+              envoyDnsRefreshRateS:
                 description: | 
-                  Corresponds to Envoy's dns_refresh_rate config field for this cluster.
+                  Corresponds to Envoy's dns_refresh_rate config field for this cluster, in seconds
                   See	https://www.envoyproxy.io/docs/envoy/latest/api-v3/config/cluster/v3/cluster.proto
-                type: string
+                type: number
               envoyRespectDnsTTL:
                 description: |
                   Corresponds to Envoy's respect_dns_ttl config field for this cluster.
diff --git a/controllers/configmap.go b/controllers/configmap.go
index 6dda795..9725d64 100644
--- a/controllers/configmap.go
+++ b/controllers/configmap.go
@@ -3,6 +3,7 @@ package controllers
 import (
 	"context"
 	"fmt"
+	"google.golang.org/protobuf/types/known/durationpb"
 	"hash/fnv"
 	"strconv"
 
@@ -298,6 +299,10 @@ func configmap(es *egressv1.ExternalService) (*corev1.ConfigMap, string, error)
 
 func generateOverrideCluster(name string, spec egressv1.ExternalServiceSpec, port egressv1.ExternalServicePort, protocol envoycorev3.SocketAddress_Protocol) *envoyv3.Cluster {
 	overrideClusterName := fmt.Sprintf("%v-override", name)
+	var dnsRefreshRate *duration.Duration
+	if spec.EnvoyDnsRefreshRateS != 0 {
+		dnsRefreshRate = &durationpb.Duration{Seconds: spec.EnvoyDnsRefreshRateS}
+	}
 	var endpoints []*envoyendpoint.LocalityLbEndpoints
 
 	for _, ip := range spec.IpOverride {
@@ -357,7 +362,7 @@ func generateOverrideCluster(name string, spec egressv1.ExternalServiceSpec, por
 			Endpoints:   endpoints,
 		},
 
-		DnsRefreshRate: spec.EnvoyDnsRefreshRate,
+		DnsRefreshRate: dnsRefreshRate,
 		RespectDnsTtl:  spec.EnvoyRespectDnsTTL,
 	}
 }