diff --git a/front/src/lib.rs b/front/src/lib.rs
index 4a2ad10..51fb3d8 100644
--- a/front/src/lib.rs
+++ b/front/src/lib.rs
@@ -13,7 +13,6 @@ pub fn main() -> Result<(), JsValue> {
 #[wasm_bindgen]
 pub fn format(before: String, path: String) -> String {
     let config = alejandra::config::Config::new();
-    let after = alejandra::format::string(&config, path, before);
 
-    return after;
+    alejandra::format::string_or_passthrough(&config, path, before)
 }
diff --git a/src/cli.rs b/src/cli.rs
index f8c9b08..b5fbf05 100644
--- a/src/cli.rs
+++ b/src/cli.rs
@@ -33,7 +33,9 @@ pub fn stdin(config: crate::config::Config) -> std::io::Result<()> {
     eprintln!("Formatting stdin, run with --help to see all options.");
     let mut stdin = String::new();
     std::io::stdin().read_to_string(&mut stdin).unwrap();
-    print!("{}", crate::format::string(&config, "stdin".to_string(), stdin));
+
+    let stdout = crate::format::string(&config, "stdin".to_string(), stdin)?;
+    print!("{}", stdout);
 
     Ok(())
 }
diff --git a/src/format.rs b/src/format.rs
index 0b725b9..3fe74d3 100644
--- a/src/format.rs
+++ b/src/format.rs
@@ -2,19 +2,33 @@ pub fn string(
     config: &crate::config::Config,
     path: String,
     string: String,
-) -> String {
+) -> std::io::Result<String> {
     let tokens = rnix::tokenizer::Tokenizer::new(&string);
     let ast = rnix::parser::parse(tokens);
 
-    for error in ast.errors() {
-        eprintln!("Error: {}, at: {}", error, path);
-        return ast.node().to_string();
+    let errors = ast.errors();
+    if !errors.is_empty() {
+        return Err(std::io::Error::new(
+            std::io::ErrorKind::InvalidInput,
+            errors[0].to_string(),
+        ));
     }
 
     let green_node =
         crate::builder::build(config, ast.node().into(), false, path).unwrap();
 
-    green_node.to_string()
+    Ok(green_node.to_string())
+}
+
+pub fn string_or_passthrough(
+    config: &crate::config::Config,
+    path: String,
+    before: String,
+) -> String {
+    match crate::format::string(&config, path, before.clone()) {
+        Ok(after) => after,
+        Err(_) => before,
+    }
 }
 
 pub fn file(
@@ -27,7 +41,7 @@ pub fn file(
     let input_clone = input.clone();
     let input_bytes = input_clone.as_bytes();
 
-    let output = crate::format::string(config, path.clone(), input);
+    let output = crate::format::string(config, path.clone(), input)?;
     let output_bytes = output.as_bytes();
 
     let changed = input_bytes != output_bytes;
diff --git a/tests/fmt.rs b/tests/fmt.rs
index b74ffb2..74f89a1 100644
--- a/tests/fmt.rs
+++ b/tests/fmt.rs
@@ -16,8 +16,11 @@ fn cases() {
         let path_in = format!("tests/cases/{}/in", case);
         let path_out = format!("tests/cases/{}/out", case);
         let content_in = std::fs::read_to_string(path_in.clone()).unwrap();
-        let content_got =
-            alejandra::format::string(&config, path_in, content_in.clone());
+        let content_got = alejandra::format::string_or_passthrough(
+            &config,
+            path_in,
+            content_in.clone(),
+        );
 
         if should_update {
             std::fs::File::create(&path_out)