diff --git a/integ/.env b/integ/.env
index ac50614..eca4ba6 100644
--- a/integ/.env
+++ b/integ/.env
@@ -3,4 +3,5 @@ ELASTICSEARCH_VERSION=7.16.2
 MYSQL_VERSION=8
 POSTGRESQL_VERSION=13
 TEMPORAL_VERSION=1.25
+TEMPORAL_ADMIN_TOOLS_VERSION=1.25.2-tctl-1.18.1-cli-1.1.1
 TEMPORAL_UI_VERSION=2.31.2
\ No newline at end of file
diff --git a/integ/docker-compose.yml b/integ/docker-compose.yml
index 8430f95..7eda69c 100644
--- a/integ/docker-compose.yml
+++ b/integ/docker-compose.yml
@@ -58,7 +58,7 @@ services:
     environment:
       - TEMPORAL_ADDRESS=temporal:7233
       - TEMPORAL_CLI_ADDRESS=temporal:7233
-    image: temporalio/admin-tools:${TEMPORAL_VERSION}
+    image: temporalio/admin-tools:${TEMPORAL_ADMIN_TOOLS_VERSION}
     networks:
       - temporal-network
     stdin_open: true
diff --git a/integ/rpc_test.go b/integ/rpc_test.go
index ba52189..314f2ed 100644
--- a/integ/rpc_test.go
+++ b/integ/rpc_test.go
@@ -30,6 +30,11 @@ func TestRPCWorkflow(t *testing.T) {
 	rpcErr, _ := err.(*iwf.ApiError)
 	assert.Equal(t, "worker API error, status:501, errorType:test-error-type", rpcErr.Response.GetDetail())
 
+	// Test unregister client
+	unregClient := iwf.NewUnregisteredClient(nil)
+	err = unregClient.InvokeRPCByName(context.Background(), wfId, "", "TestErrorRPC", 1, nil, nil)
+	assert.NotNil(t, err)
+
 	var rpcOutput int
 	err = client.InvokeRPC(context.Background(), wfId, "", wf.TestRPC, 1, &rpcOutput)
 	assert.Nil(t, err)
diff --git a/integ/workflow_uncompleted_test.go b/integ/workflow_uncompleted_test.go
index d1a94e7..836cc0d 100644
--- a/integ/workflow_uncompleted_test.go
+++ b/integ/workflow_uncompleted_test.go
@@ -112,8 +112,8 @@ func TestStateApiTimeoutWorkflow(t *testing.T) {
 
 	fmt.Println(err)
 
-	expectedMsg := "workflow is not completed successfully, closedStatus: FAILED, failedErrorType(applies if failed as closedStatus):STATE_API_FAIL_MAX_OUT_RETRY_ERROR_TYPE, error message:activity error (type: StateApiWaitUntil, scheduledEventID: 8, startedEventID: 9, identity: ): activity StartToClose timeout (type: StartToClose)"
-	assert.Equal(t, expectedMsg, err.Error())
+	expectedMsg := "workflow is not completed successfully, closedStatus: FAILED, failedErrorType(applies if failed as closedStatus):STATE_API_FAIL_MAX_OUT_RETRY_ERROR_TYPE, error message:activity error "
+	assert.True(t, strings.HasPrefix(err.Error(), expectedMsg))
 
 	out, err2 := client.GetComplexWorkflowResults(context.Background(), wfId, "")
 	assert.Nil(t, out)
diff --git a/iwf/errors.go b/iwf/errors.go
index e201ae8..489e8c7 100644
--- a/iwf/errors.go
+++ b/iwf/errors.go
@@ -171,7 +171,7 @@ func IsWorkflowNotExistsError(err error) bool {
 
 func IsRPCError(err error) bool {
 	apiError, ok := err.(*ApiError)
-	if !ok || apiError.Response == nil {
+	if !ok {
 		return false
 	}
 	return apiError.StatusCode == 420