diff --git a/go/oasis-net-runner/fixtures/default.go b/go/oasis-net-runner/fixtures/default.go
index 182e20c7e4c..5aa8ba611a0 100644
--- a/go/oasis-net-runner/fixtures/default.go
+++ b/go/oasis-net-runner/fixtures/default.go
@@ -260,6 +260,7 @@ func newDefaultFixture() (*oasis.NetworkFixture, error) {
 				fixture.ComputeWorkers[j].Runtimes = append(fixture.ComputeWorkers[j].Runtimes, rtIndex)
 			}
 			fixture.Clients[0].Runtimes = append(fixture.Clients[0].Runtimes, rtIndex)
+			fixture.Clients[0].Entity = 1
 
 			// Runtime state paths to use to initialize the runtime with.
 			if len(runtimeStatePaths) <= i {
diff --git a/go/oasis-test-runner/oasis/client.go b/go/oasis-test-runner/oasis/client.go
index 7e2e98a9d11..4d785e63e36 100644
--- a/go/oasis-test-runner/oasis/client.go
+++ b/go/oasis-test-runner/oasis/client.go
@@ -58,6 +58,11 @@ func (client *Client) ModifyConfig() error {
 
 	client.Config.P2P.Port = client.p2pPort
 
+	if !client.entity.isDebugTestEntity {
+		entityID, _ := client.entity.ID().MarshalText() // Cannot fail.
+		client.Config.Registration.EntityID = string(entityID)
+	}
+
 	if len(client.runtimes) > 0 {
 		client.Config.Mode = config.ModeClient
 		client.Config.Runtime.Provisioner = client.runtimeProvisioner
diff --git a/go/oasis-test-runner/oasis/fixture.go b/go/oasis-test-runner/oasis/fixture.go
index be60faae827..dca781db3c3 100644
--- a/go/oasis-test-runner/oasis/fixture.go
+++ b/go/oasis-test-runner/oasis/fixture.go
@@ -496,6 +496,8 @@ func (f *SentryFixture) Create(net *Network) (*Sentry, error) {
 type ClientFixture struct {
 	NodeFixture
 
+	Entity int `json:"entity"`
+
 	AllowErrorTermination bool `json:"allow_error_termination"`
 	AllowEarlyTermination bool `json:"allow_early_termination"`