diff --git a/internal/cmd/build/main.go b/internal/cmd/build/main.go
index 346c77e64..ce6932ec1 100644
--- a/internal/cmd/build/main.go
+++ b/internal/cmd/build/main.go
@@ -144,7 +144,7 @@ func (b *builder) integrationTest() error {
 				HostPort:  "127.0.0.1:7233",
 				Namespace: "integration-test-namespace",
 			},
-			LogLevel: "warn",
+			LogLevel: "error",
 			ExtraArgs: []string{
 				"--dynamic-config-value", "frontend.enableExecuteMultiOperation=true",
 				"--dynamic-config-value", "frontend.enableUpdateWorkflowExecution=true",
diff --git a/internal/internal_command_state_machine.go b/internal/internal_command_state_machine.go
index c8c90bef2..40deafd37 100644
--- a/internal/internal_command_state_machine.go
+++ b/internal/internal_command_state_machine.go
@@ -1072,13 +1072,16 @@ func (h *commandsHelper) incrementNextCommandEventIDIfVersionMarker() {
 }
 
 func (h *commandsHelper) getCommand(id commandID) commandStateMachine {
-	command, ok := h.commands[id]
+	listElem, ok := h.commands[id]
+	command := listElem.Value.(commandStateMachine)
+	commandID := command.getID()
 	if !ok {
-		panicMsg := fmt.Sprintf("[TMPRL1100] unknown command %v, possible causes are nondeterministic workflow definition code"+
-			" or incompatible change in the workflow definition", id)
+		panicMsg := fmt.Sprintf(
+			"[TMPRL1100] During replay, workflow history (event ID %s) implies that a %v command should have been emitted by the replayed code, but no such command was emitted. "+
+				"Possible causes are nondeterministic workflow definition code, or an incompatible change in the workflow definition.", commandID.id, commandID.commandType)
 		panicIllegalState(panicMsg)
 	}
-	return command.Value.(commandStateMachine)
+	return command
 }
 
 func (h *commandsHelper) addCommand(command commandStateMachine) {
diff --git a/test/integration_test.go b/test/integration_test.go
index 8a05591b3..a1637dc47 100644
--- a/test/integration_test.go
+++ b/test/integration_test.go
@@ -4591,6 +4591,8 @@ func (ts *IntegrationTestSuite) testNonDeterminismFailureCause(historyMismatch b
 		return false
 	}, 10*time.Second, 300*time.Millisecond)
 
+	ts.T().Errorf("\n\n-----------------------------------\n%v\n\n-----------------------------------\n\n", taskFailed)
+
 	// Check the task has the expected cause
 	ts.NoError(histErr)
 	ts.Equal(enumspb.WORKFLOW_TASK_FAILED_CAUSE_NON_DETERMINISTIC_ERROR, taskFailed.Cause)
@@ -4598,6 +4600,50 @@ func (ts *IntegrationTestSuite) testNonDeterminismFailureCause(historyMismatch b
 	ts.True(taskFailedMetric >= 1)
 }
 
+func (ts *IntegrationTestSuite) TestNonDeterminismFailureCauseCommandNotFound() {
+	// Create a situation in which, on replay, a TimerStarted event is
+	// encountered and yet the code emits no corresponding command.
+	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
+	defer cancel()
+
+	wfID := "test-non-determinism-failure-cause-command-not-found-" + uuid.New()
+	// Client starts workflow via UpdateWithStart and waits for update response
+	// ("early return" pattern)
+	startWfOptions := ts.startWorkflowOptions(wfID)
+	startWfOptions.WorkflowIDConflictPolicy = enumspb.WORKFLOW_ID_CONFLICT_POLICY_FAIL
+	updHandle, err := ts.client.UpdateWithStartWorkflow(ctx, client.UpdateWithStartWorkflowOptions{
+		StartWorkflowOperation: ts.client.NewWithStartWorkflowOperation(startWfOptions, ts.workflows.NonDeterminismCommandNotFoundWorkflow),
+		UpdateOptions: client.UpdateWorkflowOptions{
+			WorkflowID:   wfID,
+			UpdateName:   "wait-for-wft-completion",
+			WaitForStage: client.WorkflowUpdateStageCompleted,
+		},
+	})
+	ts.NoError(err)
+
+	// WFT 1: workflow shouldStartTimer state is true, causing workflow to
+	// emit a StartTimer command; workflow sends update response.
+	ts.NoError(updHandle.Get(ctx, nil))
+	// Stop worker and start a new one in order to force full history replay.
+	ts.worker.Stop()
+	nextWorker := worker.New(ts.client, ts.taskQueueName, worker.Options{WorkflowPanicPolicy: internal.FailWorkflow})
+	ts.registerWorkflowsAndActivities(nextWorker)
+	ts.NoError(nextWorker.Start())
+	defer nextWorker.Stop()
+	// Set shouldStartTimer=false and send second update in order to trigger a
+	// WFT.
+	shouldStartTimer = false
+	updHandle, err = ts.client.UpdateWorkflow(ctx, client.UpdateWorkflowOptions{
+		WorkflowID:   wfID,
+		UpdateName:   "wait-for-wft-completion",
+		WaitForStage: client.WorkflowUpdateStageCompleted,
+	})
+	ts.NoError(err)
+	// WFT 2: full replay, NDE due to missing StartTimer command.
+	err = updHandle.Get(ctx, nil)
+	ts.T().Logf("\n\n-----------------------------------\n%v\n\n-----------------------------------\n\n", err)
+}
+
 func (ts *IntegrationTestSuite) TestNonDeterminismFailureCauseReplay() {
 	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
 	defer cancel()
diff --git a/test/workflow_test.go b/test/workflow_test.go
index 53aae82dd..ba87e508d 100644
--- a/test/workflow_test.go
+++ b/test/workflow_test.go
@@ -2831,6 +2831,18 @@ func (w *Workflows) ForcedNonDeterminism(ctx workflow.Context, sameCommandButDif
 	return
 }
 
+var shouldStartTimer = true
+
+func (w *Workflows) NonDeterminismCommandNotFoundWorkflow(ctx workflow.Context) error {
+	workflow.SetUpdateHandler(ctx, "wait-for-wft-completion", func(ctx workflow.Context) error {
+		return nil
+	})
+	if shouldStartTimer {
+		workflow.Sleep(ctx, 999*time.Hour)
+	}
+	return nil
+}
+
 func (w *Workflows) NonDeterminismReplay(ctx workflow.Context) error {
 	ctx = workflow.WithActivityOptions(ctx, w.defaultActivityOptions())
 	var a Activities
@@ -3471,6 +3483,7 @@ func (w *Workflows) register(worker worker.Worker) {
 	worker.RegisterWorkflow(w.SignalCounter)
 	worker.RegisterWorkflow(w.PanicOnSignal)
 	worker.RegisterWorkflow(w.ForcedNonDeterminism)
+	worker.RegisterWorkflow(w.NonDeterminismCommandNotFoundWorkflow)
 	worker.RegisterWorkflow(w.NonDeterminismReplay)
 	worker.RegisterWorkflow(w.MutableSideEffect)
 	worker.RegisterWorkflow(w.HistoryLengths)
@@ -3496,7 +3509,6 @@ func (w *Workflows) register(worker worker.Worker) {
 	worker.RegisterWorkflow(w.AwaitWithOptions)
 	worker.RegisterWorkflow(w.WorkflowWithRejectableUpdate)
 	worker.RegisterWorkflow(w.WorkflowWithUpdate)
-
 	worker.RegisterWorkflow(w.child)
 	worker.RegisterWorkflow(w.childWithRetryPolicy)
 	worker.RegisterWorkflow(w.childWithCustomRetryPolicy)