diff --git a/src/HOTP.php b/src/HOTP.php
index e6bea73..adcbdfa 100644
--- a/src/HOTP.php
+++ b/src/HOTP.php
@@ -41,9 +41,9 @@ public static function createFromSecret(string $secret): self
         return $htop;
     }
 
-    public static function generate(): self
+    public static function generate(int $secretSize = null): self
     {
-        return self::createFromSecret(self::generateSecret());
+        return self::createFromSecret(self::generateSecret($secretSize));
     }
 
     public function getCounter(): int
diff --git a/src/OTP.php b/src/OTP.php
index 49e1730..0f981d2 100644
--- a/src/OTP.php
+++ b/src/OTP.php
@@ -43,9 +43,9 @@ public function at(int $input): string
     /**
      * @return non-empty-string
      */
-    final protected static function generateSecret(): string
+    final protected static function generateSecret(int $secretSize = null): string
     {
-        return Base32::encodeUpper(random_bytes(self::DEFAULT_SECRET_SIZE));
+        return Base32::encodeUpper(random_bytes($secretSize ?? self::DEFAULT_SECRET_SIZE));
     }
 
     /**
diff --git a/src/TOTP.php b/src/TOTP.php
index 6bc87ee..beb1611 100644
--- a/src/TOTP.php
+++ b/src/TOTP.php
@@ -62,9 +62,9 @@ public static function createFromSecret(string $secret, ?ClockInterface $clock =
         return $totp;
     }
 
-    public static function generate(?ClockInterface $clock = null): self
+    public static function generate(?ClockInterface $clock = null, int $secretSize = null): self
     {
-        return self::createFromSecret(self::generateSecret(), $clock);
+        return self::createFromSecret(self::generateSecret($secretSize), $clock);
     }
 
     public function getPeriod(): int