diff --git a/cmd/slackdump/main.go b/cmd/slackdump/main.go
index 5abe2d14..6ef70512 100644
--- a/cmd/slackdump/main.go
+++ b/cmd/slackdump/main.go
@@ -22,6 +22,8 @@ const (
 	slackCookieEnv = "COOKIE"
 )
 
+const defFilenameTemplate = "{{.ID}}{{ if .ThreadTS}}-{{.ThreadTS}}{{end}}"
+
 var build = "dev"
 
 // secrets defines the names of the supported secret files that we load our
@@ -136,7 +138,7 @@ func parseCmdLine(args []string) (params, error) {
 	fs.StringVar(&p.appCfg.Output.Filename, "o", "-", "Output `filename` for users and channels.  Use '-' for standard\nOutput.")
 	fs.StringVar(&p.appCfg.Output.Format, "r", "", "report `format`.  One of 'json' or 'text'")
 
-	fs.StringVar(&p.appCfg.FilenameTemplate, "ft", "{{.ID}}{{ if .ThreadTS}}-{{.ThreadTS}}{{end}}", "output file naming template.")
+	fs.StringVar(&p.appCfg.FilenameTemplate, "ft", defFilenameTemplate, "output file naming template.")
 
 	// options
 	fs.BoolVar(&p.appCfg.Options.DumpFiles, "f", slackdump.DefOptions.DumpFiles, "same as -download")
diff --git a/cmd/slackdump/main_test.go b/cmd/slackdump/main_test.go
index a77f6ca6..c0980ffc 100644
--- a/cmd/slackdump/main_test.go
+++ b/cmd/slackdump/main_test.go
@@ -59,9 +59,10 @@ func Test_checkParameters(t *testing.T) {
 					Token:  "x",
 					Cookie: "d",
 				},
-				Input:   app.Input{List: []string{}},
-				Output:  app.Output{Filename: "-", Format: "text"},
-				Options: slackdump.DefOptions,
+				FilenameTemplate: defFilenameTemplate,
+				Input:            app.Input{List: []string{}},
+				Output:           app.Output{Filename: "-", Format: "text"},
+				Options:          slackdump.DefOptions,
 			}},
 			false,
 		},
@@ -77,9 +78,10 @@ func Test_checkParameters(t *testing.T) {
 					Token:  "x",
 					Cookie: "d",
 				},
-				Input:   app.Input{List: []string{}},
-				Output:  app.Output{Filename: "-", Format: "text"},
-				Options: slackdump.DefOptions,
+				FilenameTemplate: defFilenameTemplate,
+				Input:            app.Input{List: []string{}},
+				Output:           app.Output{Filename: "-", Format: "text"},
+				Options:          slackdump.DefOptions,
 			}},
 			false,
 		},
diff --git a/internal/app/app.go b/internal/app/app.go
index 529ed846..2c077dc2 100644
--- a/internal/app/app.go
+++ b/internal/app/app.go
@@ -4,6 +4,7 @@ import (
 	"context"
 	"encoding/json"
 	"errors"
+	"html/template"
 	"io"
 	"os"
 	"strings"
@@ -19,14 +20,22 @@ const (
 )
 
 type App struct {
-	sd *slackdump.SlackDumper
+	sd   *slackdump.SlackDumper
+	tmpl *template.Template
 
 	cfg Config
 }
 
 // New creates a new slackdump app.
 func New(cfg Config) (*App, error) {
-	return &App{cfg: cfg}, nil
+	if err := cfg.Validate(); err != nil {
+		return nil, err
+	}
+	tmpl, err := cfg.compileTemplates()
+	if err != nil {
+		return nil, err
+	}
+	return &App{cfg: cfg, tmpl: tmpl}, nil
 }
 
 // init initialises the slack dumper app.
@@ -107,7 +116,7 @@ func (app *App) newDumpFunc(s string) dumpFunc {
 
 func (app *App) renderFilename(c *slackdump.Conversation) string {
 	var buf strings.Builder
-	if err := app.cfg.tmpl.ExecuteTemplate(&buf, filenameTmplName, c); err != nil {
+	if err := app.tmpl.ExecuteTemplate(&buf, filenameTmplName, c); err != nil {
 		// this should nevar happen
 		panic(err)
 	}
diff --git a/internal/app/config.go b/internal/app/config.go
index f45979ea..2271d595 100644
--- a/internal/app/config.go
+++ b/internal/app/config.go
@@ -25,7 +25,6 @@ type Config struct {
 	Latest TimeValue // latest time to dump conversations to
 
 	FilenameTemplate string
-	tmpl             *template.Template
 
 	Options slackdump.Options
 }
@@ -125,13 +124,15 @@ func (p *Config) Validate() error {
 	return nil
 }
 
-func (p *Config) compileValidateTemplate() error {
-	var err error
-	p.tmpl, err = template.New(filenameTmplName).Parse(p.FilenameTemplate)
+func (cfg *Config) compileTemplates() (*template.Template, error) {
+	return template.New(filenameTmplName).Parse(cfg.FilenameTemplate)
+}
+
+func (cfg *Config) compileValidateTemplate() error {
+	tmpl, err := cfg.compileTemplates()
 	if err != nil {
 		return err
 	}
-
 	// are you ready for some filth? Here we go!
 
 	// let's define some indicators
@@ -152,15 +153,15 @@ func (p *Config) compileValidateTemplate() error {
 
 	// now we render the template and check for OK/NotOK values in the output.
 	var buf strings.Builder
-	if err := p.tmpl.ExecuteTemplate(&buf, filenameTmplName, tc); err != nil {
+	if err := tmpl.ExecuteTemplate(&buf, filenameTmplName, tc); err != nil {
 		return err
 	}
 	if strings.Contains(buf.String(), NotOK) || len(buf.String()) == 0 {
-		return fmt.Errorf("invalid fields in the template: %q", p.FilenameTemplate)
+		return fmt.Errorf("invalid fields in the template: %q", cfg.FilenameTemplate)
 	}
 	if !strings.Contains(buf.String(), OK) {
 		// must contain at least one OK
-		return fmt.Errorf("this does not resolve to anything useful: %q", p.FilenameTemplate)
+		return fmt.Errorf("this does not resolve to anything useful: %q", cfg.FilenameTemplate)
 	}
 	return nil
 }
diff --git a/internal/app/config_test.go b/internal/app/config_test.go
index 3644a8c8..796c02d6 100644
--- a/internal/app/config_test.go
+++ b/internal/app/config_test.go
@@ -1,7 +1,6 @@
 package app
 
 import (
-	"html/template"
 	"testing"
 
 	"github.com/rusq/slackdump"
@@ -16,7 +15,6 @@ func TestConfig_compileValidateTemplate(t *testing.T) {
 		Oldest           TimeValue
 		Latest           TimeValue
 		FilenameTemplate string
-		tmpl             *template.Template
 		Options          slackdump.Options
 	}
 	tests := []struct {
@@ -26,42 +24,42 @@ func TestConfig_compileValidateTemplate(t *testing.T) {
 	}{
 		{
 			"id is ok",
-			fields{FilenameTemplate: "{{.ID}}", tmpl: template.New("")},
+			fields{FilenameTemplate: "{{.ID}}"},
 			false,
 		},
 		{
 			"name is ok",
-			fields{FilenameTemplate: "{{.Name}}", tmpl: template.New("")},
+			fields{FilenameTemplate: "{{.Name}}"},
 			false,
 		},
 		{
 			"just threadTS is not ok",
-			fields{FilenameTemplate: "{{.ThreadTS}}", tmpl: template.New("")},
+			fields{FilenameTemplate: "{{.ThreadTS}}"},
 			true,
 		},
 		{
 			"threadTS and message ID is ok",
-			fields{FilenameTemplate: "{{.ID}}-{{.ThreadTS}}", tmpl: template.New("")},
+			fields{FilenameTemplate: "{{.ID}}-{{.ThreadTS}}"},
 			false,
 		},
 		{
 			"threadTS and message ID is ok (conditional)",
-			fields{FilenameTemplate: "{{.ID}}{{ if .ThreadTS}}-{{.ThreadTS}}{{end}}", tmpl: template.New("")},
+			fields{FilenameTemplate: "{{.ID}}{{ if .ThreadTS}}-{{.ThreadTS}}{{end}}"},
 			false,
 		},
 		{
 			"message is not ok",
-			fields{FilenameTemplate: "{{.Message}}", tmpl: template.New("")},
+			fields{FilenameTemplate: "{{.Message}}"},
 			true,
 		},
 		{
 			"unknown field is not ok",
-			fields{FilenameTemplate: "{{.Who_dis}}", tmpl: template.New("")},
+			fields{FilenameTemplate: "{{.Who_dis}}"},
 			true,
 		},
 		{
 			"empty not ok",
-			fields{FilenameTemplate: "", tmpl: template.New("")},
+			fields{FilenameTemplate: ""},
 			true,
 		},
 	}
@@ -75,7 +73,6 @@ func TestConfig_compileValidateTemplate(t *testing.T) {
 				Oldest:           tt.fields.Oldest,
 				Latest:           tt.fields.Latest,
 				FilenameTemplate: tt.fields.FilenameTemplate,
-				tmpl:             tt.fields.tmpl,
 				Options:          tt.fields.Options,
 			}
 			if err := p.compileValidateTemplate(); (err != nil) != tt.wantErr {