diff --git a/fishctl/src/command/config/update/v1.rs b/fishctl/src/command/config/update/v1.rs
index b23c167..f306e49 100644
--- a/fishctl/src/command/config/update/v1.rs
+++ b/fishctl/src/command/config/update/v1.rs
@@ -250,7 +250,9 @@ async fn read_old_config(base_dir: &Path) -> Result<(HashMap<String, Yaml>, Meta
             .ok_or(Error::InvalidConfig("db.host"))?,
         db.get(&Yaml::String("port".to_string()))
             .and_then(|v| v.as_i64())
-            .ok_or(Error::InvalidConfig("db.port"))? as u16,
+            .ok_or(Error::InvalidConfig("db.port"))?
+            .try_into()
+            .map_err(|_| Error::InvalidConfig("Invalid `db.port` number"))?,
         db.get(&Yaml::String("user".to_string()))
             .and_then(|v| v.as_str())
             .ok_or(Error::InvalidConfig("db.user"))?,
@@ -311,9 +313,13 @@ fn create_new_server_config(
         let id = id.as_hash().ok_or(Error::InvalidConfig("cuid"))?;
         Some(server::Id {
             length: match id.get(&Yaml::String("length".to_string())) {
-                Some(length) => {
-                    Some(length.as_i64().ok_or(Error::InvalidConfig("cuid.length"))? as u8)
-                }
+                Some(length) => Some(
+                    length
+                        .as_i64()
+                        .ok_or(Error::InvalidConfig("cuid.length"))?
+                        .try_into()
+                        .map_err(|_| Error::InvalidConfig("Invalid `cuid.length` number"))?,
+                ),
                 None => None,
             },
             fingerprint: match id.get(&Yaml::String("fingerprint".to_string())) {
@@ -342,7 +348,9 @@ fn create_new_server_config(
                 .as_i64()
                 .ok_or(Error::InvalidConfig("`maxFileSize` is not an integer"))?
                 / 1_000_000;
-            file.max_size = Some(max_size_mb as u64);
+            file.max_size = Some(max_size_mb.try_into().map_err(|_| {
+                Error::InvalidConfig("Invalid `maxFileSize` number (negative or too big)")
+            })?);
         }
         if let Some(proxy_remote_files) = default_yml.get("proxyRemoteFiles") {
             let proxy_remote_files = proxy_remote_files.as_bool().ok_or(Error::InvalidConfig(
@@ -424,7 +432,7 @@ fn create_new_server_config(
         None => None,
     };
 
-    let mut server_config = server::Config {
+    let server_config = server::Config {
         config_revision: Revision::V1,
         server_info: Some(server::ServerInfo {
             name: meta.name.to_owned(),
@@ -456,7 +464,9 @@ fn create_new_server_config(
                 port: default_yml
                     .get("port")
                     .and_then(|v| v.as_i64())
-                    .ok_or(Error::InvalidConfig("port"))? as u16,
+                    .ok_or(Error::InvalidConfig("port"))?
+                    .try_into()
+                    .map_err(|_| Error::InvalidConfig("Invalid `port` number"))?,
             },
             http_proxy,
             media_proxy,
@@ -472,7 +482,9 @@ fn create_new_server_config(
             port: db
                 .get(&Yaml::String("port".to_string()))
                 .and_then(|v| v.as_i64())
-                .ok_or(Error::InvalidConfig("db.port"))? as u16,
+                .ok_or(Error::InvalidConfig("db.port"))?
+                .try_into()
+                .map_err(|_| Error::InvalidConfig("Invalid `db.port` number"))?,
             user: db
                 .get(&Yaml::String("user".to_string()))
                 .and_then(|v| v.as_str())
@@ -498,7 +510,9 @@ fn create_new_server_config(
             port: redis
                 .get(&Yaml::String("port".to_string()))
                 .and_then(|v| v.as_i64())
-                .ok_or(Error::InvalidConfig("redis.port"))? as u16,
+                .ok_or(Error::InvalidConfig("redis.port"))?
+                .try_into()
+                .map_err(|_| Error::InvalidConfig("Invalid `redis.port` number"))?,
             user: match redis.get(&Yaml::String("user".to_string())) {
                 Some(user) => Some(
                     user.as_str()
@@ -516,7 +530,12 @@ fn create_new_server_config(
                 None => None,
             },
             index: match redis.get(&Yaml::String("db".to_string())) {
-                Some(db) => Some(db.as_i64().ok_or(Error::InvalidConfig("redis.db"))? as u8),
+                Some(db) => Some(
+                    db.as_i64()
+                        .ok_or(Error::InvalidConfig("redis.db"))?
+                        .try_into()
+                        .map_err(|_| Error::InvalidConfig("Invalid `redis.db` number"))?,
+                ),
                 None => None,
             },
             prefix: match redis.get(&Yaml::String("prefix".to_string())) {