diff --git a/Cargo.lock b/Cargo.lock
index f742def..a20bdcc 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -517,6 +517,7 @@ dependencies = [
  "regex",
  "rsa",
  "sha1",
+ "thiserror",
 ]
 
 [[package]]
@@ -596,6 +597,26 @@ dependencies = [
  "unicode-ident",
 ]
 
+[[package]]
+name = "thiserror"
+version = "2.0.12"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "567b8a2dae586314f7be2a752ec7474332959c6460e02bde30d702a66d488708"
+dependencies = [
+ "thiserror-impl",
+]
+
+[[package]]
+name = "thiserror-impl"
+version = "2.0.12"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7f7cf42b4507d8ea322120659672cf1b9dbb93f8f2d4ecfd6e51350ff5b17a1d"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "typenum"
 version = "1.18.0"
diff --git a/Cargo.toml b/Cargo.toml
index 2d38ed6..c933993 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -34,3 +34,4 @@ glob = "0"
 regex = "1"
 clap = { version = "4", features = ["derive"] }
 anyhow = "1"
+thiserror = "2"
diff --git a/src/bin/rustii/title/wad.rs b/src/bin/rustii/title/wad.rs
index 239b4f0..424e73a 100644
--- a/src/bin/rustii/title/wad.rs
+++ b/src/bin/rustii/title/wad.rs
@@ -117,21 +117,21 @@ pub fn convert_wad(input: &str, target: &ConvertTargets, output: &Option<String>
         Target::Dev => {
             title.tmd.set_signature_issuer(String::from("Root-CA00000002-CP00000007"))?;
             title.ticket.set_signature_issuer(String::from("Root-CA00000002-XS00000006"))?;
-            title_key_new = crypto::encrypt_title_key(title_key, 0, title.ticket.title_id, Some(true));
+            title_key_new = crypto::encrypt_title_key(title_key, 0, title.ticket.title_id, true);
             title.ticket.common_key_index = 0;
             title.tmd.is_vwii = 0;
         },
         Target::Retail => {
             title.tmd.set_signature_issuer(String::from("Root-CA00000001-CP00000004"))?;
             title.ticket.set_signature_issuer(String::from("Root-CA00000001-XS00000003"))?;
-            title_key_new = crypto::encrypt_title_key(title_key, 0, title.ticket.title_id, Some(false));
+            title_key_new = crypto::encrypt_title_key(title_key, 0, title.ticket.title_id, false);
             title.ticket.common_key_index = 0;
             title.tmd.is_vwii = 0;
         },
         Target::Vwii => {
             title.tmd.set_signature_issuer(String::from("Root-CA00000001-CP00000004"))?;
             title.ticket.set_signature_issuer(String::from("Root-CA00000001-XS00000003"))?;
-            title_key_new = crypto::encrypt_title_key(title_key, 2, title.ticket.title_id, Some(false));
+            title_key_new = crypto::encrypt_title_key(title_key, 2, title.ticket.title_id, false);
             title.ticket.common_key_index = 2;
             title.tmd.is_vwii = 1;
         }
diff --git a/src/title/commonkeys.rs b/src/title/commonkeys.rs
index 9697c09..c7ccea9 100644
--- a/src/title/commonkeys.rs
+++ b/src/title/commonkeys.rs
@@ -8,7 +8,7 @@ const DEV_COMMON_KEY: &str = "a1604a6a7123b529ae8bec32c816fcaa";
 
 /// Returns the common key for the specified index. Providing Some(true) for the optional argument
 /// is_dev will make index 0 return the development common key instead of the retail common key.
-pub fn get_common_key(index: u8, is_dev: Option<bool>) -> [u8; 16] {
+pub fn get_common_key(index: u8, is_dev: bool) -> [u8; 16] {
     // Match the Korean and vWii keys, and if they don't match then fall back on the common key.
     // The is_dev argument is an option, and if it's set to false or None, then the regular
     // common key will be used.
@@ -18,8 +18,8 @@ pub fn get_common_key(index: u8, is_dev: Option<bool>) -> [u8; 16] {
         2 => selected_key = VWII_KEY,
         _ => {
             match is_dev {
-                Some(true) => selected_key = DEV_COMMON_KEY,
-                _ => selected_key = COMMON_KEY,
+                true => selected_key = DEV_COMMON_KEY,
+                false => selected_key = COMMON_KEY,
             }
         }
     }
@@ -32,22 +32,22 @@ mod tests {
 
     #[test]
     fn test_get_common_key() {
-        assert_eq!(get_common_key(0, None), [0xeb, 0xe4, 0x2a, 0x22, 0x5e, 0x85, 0x93, 0xe4, 0x48, 0xd9, 0xc5, 0x45, 0x73, 0x81, 0xaa, 0xf7]);
+        assert_eq!(get_common_key(0, false), [0xeb, 0xe4, 0x2a, 0x22, 0x5e, 0x85, 0x93, 0xe4, 0x48, 0xd9, 0xc5, 0x45, 0x73, 0x81, 0xaa, 0xf7]);
     }
     #[test]
     fn test_get_invalid_index() {
-        assert_eq!(get_common_key(57, None), [0xeb, 0xe4, 0x2a, 0x22, 0x5e, 0x85, 0x93, 0xe4, 0x48, 0xd9, 0xc5, 0x45, 0x73, 0x81, 0xaa, 0xf7]);
+        assert_eq!(get_common_key(57, false), [0xeb, 0xe4, 0x2a, 0x22, 0x5e, 0x85, 0x93, 0xe4, 0x48, 0xd9, 0xc5, 0x45, 0x73, 0x81, 0xaa, 0xf7]);
     }
     #[test]
     fn test_get_korean_key() {
-        assert_eq!(get_common_key(1, None), [0x63, 0xb8, 0x2b, 0xb4, 0xf4, 0x61, 0x4e, 0x2e, 0x13, 0xf2, 0xfe, 0xfb, 0xba, 0x4c, 0x9b, 0x7e]);
+        assert_eq!(get_common_key(1, false), [0x63, 0xb8, 0x2b, 0xb4, 0xf4, 0x61, 0x4e, 0x2e, 0x13, 0xf2, 0xfe, 0xfb, 0xba, 0x4c, 0x9b, 0x7e]);
     }
     #[test]
     fn test_get_vwii_key() {
-        assert_eq!(get_common_key(2, None), [0x30, 0xbf, 0xc7, 0x6e, 0x7c, 0x19, 0xaf, 0xbb, 0x23, 0x16, 0x33, 0x30, 0xce, 0xd7, 0xc2, 0x8d]);
+        assert_eq!(get_common_key(2, false), [0x30, 0xbf, 0xc7, 0x6e, 0x7c, 0x19, 0xaf, 0xbb, 0x23, 0x16, 0x33, 0x30, 0xce, 0xd7, 0xc2, 0x8d]);
     }
     #[test]
     fn test_get_dev_key() {
-        assert_eq!(get_common_key(0, Some(true)), [0xa1, 0x60, 0x4a, 0x6a, 0x71, 0x23, 0xb5, 0x29, 0xae, 0x8b, 0xec, 0x32, 0xc8, 0x16, 0xfc, 0xaa]);
+        assert_eq!(get_common_key(0, true), [0xa1, 0x60, 0x4a, 0x6a, 0x71, 0x23, 0xb5, 0x29, 0xae, 0x8b, 0xec, 0x32, 0xc8, 0x16, 0xfc, 0xaa]);
     }
 }
diff --git a/src/title/crypto.rs b/src/title/crypto.rs
index 2e0befc..58d9625 100644
--- a/src/title/crypto.rs
+++ b/src/title/crypto.rs
@@ -15,7 +15,7 @@ fn title_id_to_iv(title_id: [u8; 8]) -> [u8; 16] {
 }
 
 /// Decrypts a Title Key using the specified common key and the corresponding Title ID.
-pub fn decrypt_title_key(title_key_enc: [u8; 16], common_key_index: u8, title_id: [u8; 8], is_dev: Option<bool>) -> [u8; 16] {
+pub fn decrypt_title_key(title_key_enc: [u8; 16], common_key_index: u8, title_id: [u8; 8], is_dev: bool) -> [u8; 16] {
     let iv = title_id_to_iv(title_id);
     type Aes128CbcDec = cbc::Decryptor<aes::Aes128>;
     let decryptor = Aes128CbcDec::new(&get_common_key(common_key_index, is_dev).into(), &iv.into());
@@ -25,7 +25,7 @@ pub fn decrypt_title_key(title_key_enc: [u8; 16], common_key_index: u8, title_id
 }
 
 /// Encrypts a Title Key using the specified common key and the corresponding Title ID.
-pub fn encrypt_title_key(title_key_dec: [u8; 16], common_key_index: u8, title_id: [u8; 8], is_dev: Option<bool>) -> [u8; 16] {
+pub fn encrypt_title_key(title_key_dec: [u8; 16], common_key_index: u8, title_id: [u8; 8], is_dev: bool) -> [u8; 16] {
     let iv = title_id_to_iv(title_id);
     type Aes128CbcEnc = cbc::Encryptor<aes::Aes128>;
     let encryptor = Aes128CbcEnc::new(&get_common_key(common_key_index, is_dev).into(), &iv.into());
diff --git a/src/title/ticket.rs b/src/title/ticket.rs
index dea23ea..0e5fe93 100644
--- a/src/title/ticket.rs
+++ b/src/title/ticket.rs
@@ -185,7 +185,7 @@ impl Ticket {
     pub fn dec_title_key(&self) -> [u8; 16] {
         // Get the dev status of this Ticket so decrypt_title_key knows the right common key.
         let is_dev = self.is_dev();
-        decrypt_title_key(self.title_key, self.common_key_index, self.title_id, Some(is_dev))
+        decrypt_title_key(self.title_key, self.common_key_index, self.title_id, is_dev)
     }
     
     /// Gets whether a Ticket was signed for development (true) or retail (false).