diff --git a/internal/configuration/settings/openvpn.go b/internal/configuration/settings/openvpn.go
index 031fef95..2824d28e 100644
--- a/internal/configuration/settings/openvpn.go
+++ b/internal/configuration/settings/openvpn.go
@@ -8,6 +8,7 @@ import (
 	"github.com/qdm12/gluetun/internal/configuration/settings/helpers"
 	"github.com/qdm12/gluetun/internal/constants"
 	"github.com/qdm12/gluetun/internal/constants/providers"
+	"github.com/qdm12/gluetun/internal/openvpn/extract"
 	"github.com/qdm12/gluetun/internal/openvpn/parse"
 	"github.com/qdm12/gotree"
 )
@@ -147,6 +148,12 @@ func validateOpenVPNConfigFilepath(isCustom bool,
 		return err
 	}
 
+	extractor := extract.New()
+	_, _, err = extractor.Data(confFile)
+	if err != nil {
+		return fmt.Errorf("failed extracting information from custom configuration file: %w", err)
+	}
+
 	return nil
 }
 
diff --git a/internal/provider/custom/openvpnconf.go b/internal/provider/custom/openvpnconf.go
index 7c0f692e..110d479e 100644
--- a/internal/provider/custom/openvpnconf.go
+++ b/internal/provider/custom/openvpnconf.go
@@ -18,7 +18,10 @@ func (p *Provider) BuildConf(connection models.Connection,
 	settings settings.OpenVPN) (lines []string, err error) {
 	lines, _, err = p.extractor.Data(*settings.ConfFile)
 	if err != nil {
-		return nil, fmt.Errorf("failed extracting information from custom configuration file: %w", err)
+		// Configuration file is already validated in settings validation in
+		// internal/configuration/settings/openvpn.go in `validateOpenVPNConfigFilepath`.
+		// Therefore this error is the result of a programming error.
+		panic(fmt.Sprintf("failed extracting information from custom configuration file: %s", err))
 	}
 
 	lines = modifyConfig(lines, connection, settings)