diff --git a/Cargo.lock b/Cargo.lock
index 88998a3..70587c2 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -262,9 +262,10 @@ checksum = "cf1de2fe8c75bc145a2f577add951f8134889b4795d47466a54a5c846d691693"
 
 [[package]]
 name = "blackd-client"
-version = "0.0.3"
+version = "0.0.4"
 dependencies = [
  "clap",
+ "custom_error",
  "httpmock",
  "minreq",
  "pretty_assertions",
@@ -436,6 +437,12 @@ dependencies = [
  "winapi",
 ]
 
+[[package]]
+name = "custom_error"
+version = "1.9.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4f8a51dd197fa6ba5b4dc98a990a43cc13693c23eb0089ebb0fcc1f04152bca6"
+
 [[package]]
 name = "diff"
 version = "0.1.12"
diff --git a/Cargo.toml b/Cargo.toml
index bd18124..f5518af 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "blackd-client"
-version = "0.0.3"
+version = "0.0.4"
 authors = ["disrupted <hi@salomonpopp.me>"]
 edition = "2018"
 description = "Blazing fast Python code formatting using Black"
@@ -13,6 +13,7 @@ categories = ["command-line-utilities"]
 [dependencies]
 minreq = "2.3.1" 
 clap = "3.0.0-beta.2"
+custom_error = "1.9.2"
 
 [dev-dependencies]
 httpmock = "0.5.8"
diff --git a/README.md b/README.md
index d1ae9a6..505acad 100644
--- a/README.md
+++ b/README.md
@@ -10,8 +10,6 @@ Luckily there's [blackd](https://black.readthedocs.io/en/stable/usage_and_config
 
 If you're using Black (or writing Python code in general) I recommend you to check it out!
 
-> this is very early stage and experimental. It's literally < 50 LOC I hacked together in one evening, and I'll probably improve it as I learn more about Rust.
-
 ## Install
 
 1. Install Black
diff --git a/src/main.rs b/src/main.rs
index 099a138..aadb5b7 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,4 +1,5 @@
 use clap::{crate_version, AppSettings, Clap};
+use custom_error::custom_error;
 use std::{io, io::prelude::*};
 
 /// Tiny HTTP client for the Black (blackd) Python code formatter
@@ -6,17 +7,28 @@ use std::{io, io::prelude::*};
 #[clap(version = crate_version!())]
 #[clap(setting = AppSettings::ColoredHelp)]
 struct Opts {
+    /// URL of blackd server
     #[clap(long, default_value = "http://localhost:45484")]
     url: String,
 }
 
+custom_error! {BlackdError
+    Minreq{source: minreq::Error} = "{source}",
+    Syntax{details: String} = "Syntax Error: {details}",
+    Formatting{details: String} = "Formatting Error: {details}",
+    Unknown{status_code: i32, body: String} = "Unknown Error: {status_code}",
+}
+
 fn main() {
     let opts: Opts = Opts::parse();
     let stdin = read_stdin();
     let result = format(opts.url, stdin.unwrap());
     match result {
         Ok(v) => print!("{}", v),
-        Err(e) => print!("Error formatting with blackd-client: {}", e),
+        Err(e) => {
+            eprint!("Error formatting with blackd-client: {}", e);
+            std::process::exit(1);
+        }
     }
 }
 
@@ -30,17 +42,23 @@ fn read_stdin() -> Result<String, Box<dyn std::error::Error + Send + Sync>> {
     Ok(buffer)
 }
 
-fn format(url: String, stdin: String) -> Result<String, minreq::Error> {
+fn format(url: String, stdin: String) -> Result<String, BlackdError> {
     let resp = minreq::post(url)
         .with_header("X-Fast-Or-Safe", "fast")
         .with_header("Content-Type", "text/plain; charset=utf-8")
         .with_body(stdin.as_str())
         .send()?;
 
+    let body = resp.as_str()?.to_string();
     match resp.status_code {
-        204 => Ok(stdin),                      // input is already well-formatted
-        200 => Ok(resp.as_str()?.to_string()), // input was reformatted by Black
-        _ => Err(minreq::Error::Other("Error")),
+        200 => Ok(body),  // input was reformatted by Black
+        204 => Ok(stdin), // input is already well-formatted
+        400 => Err(BlackdError::Syntax { details: body }),
+        500 => Err(BlackdError::Formatting { details: body }),
+        _ => Err(BlackdError::Unknown {
+            status_code: resp.status_code,
+            body,
+        }),
     }
 }
 
@@ -87,7 +105,45 @@ mod tests {
     }
 
     #[test]
-    fn test_format_error() {
+    fn test_syntax_error() {
+        let server = MockServer::start();
+        let mock = server.mock(|when, then| {
+            when.method("POST");
+            then.status(400)
+                .body("Cannot parse: 1:6: print('bad syntax'))");
+        });
+
+        let result = format(server.url(""), "print('bad syntax'))".to_string());
+
+        mock.assert();
+        assert!(result.is_err());
+        assert_eq!(
+            result.unwrap_err().to_string(),
+            "Syntax Error: Cannot parse: 1:6: print('bad syntax'))"
+        );
+    }
+
+    #[test]
+    fn test_formatting_error() {
+        let server = MockServer::start();
+        let mock = server.mock(|when, then| {
+            when.method("POST");
+            then.status(500)
+                .body("('EOF in multi-line statement', (2, 0))");
+        });
+
+        let result = format(server.url(""), "print(('bad syntax')".to_string());
+
+        mock.assert();
+        assert!(result.is_err());
+        assert_eq!(
+            result.unwrap_err().to_string(),
+            "Formatting Error: ('EOF in multi-line statement', (2, 0))"
+        );
+    }
+
+    #[test]
+    fn test_unknown_error() {
         let server = MockServer::start();
         let mock = server.mock(|when, then| {
             when.method("POST");
@@ -98,5 +154,6 @@ mod tests {
 
         mock.assert();
         assert!(result.is_err());
+        assert_eq!(result.unwrap_err().to_string(), "Unknown Error: 418");
     }
 }