diff --git a/pkg/config/config.go b/pkg/config/config.go
index 465677a16..3877f32f6 100644
--- a/pkg/config/config.go
+++ b/pkg/config/config.go
@@ -304,7 +304,7 @@ type (
 
 	phoneFactorTypeConfiguration struct {
 		factorTypeConfiguration
-		OtpLength    int           `toml:"otp_length"`
+		OtpLength    uint          `toml:"otp_length"`
 		Template     string        `toml:"template"`
 		MaxFrequency time.Duration `toml:"max_frequency"`
 	}