diff --git a/src/class.rs b/src/class.rs
index 1dfa52d..7159c7d 100644
--- a/src/class.rs
+++ b/src/class.rs
@@ -1,4 +1,4 @@
-use crate::Zephyr;
+use crate::{Zephyr, ZephyrError};
 
 #[derive(PartialEq, Debug)]
 pub(crate) struct Class<'a> {
@@ -56,7 +56,7 @@ impl<'a> Class<'a> {
         r
     }
 
-    pub(crate) fn generate(&self, z: &Zephyr) -> Result<String, &'static str> {
+    pub(crate) fn generate(&self, z: &Zephyr) -> Result<String, ZephyrError> {
         let name = z
             .names
             .get(self.name)
@@ -84,7 +84,7 @@ impl<'a> Class<'a> {
         } else if let Some(v) = z.rules.get(name) {
             Ok(format!("{selector}{{{v}}}"))
         } else {
-            Err("{name} is not a no-variable rule, and no variables were provided")
+            Err(ZephyrError::ValueMissing)
         }
     }
 }
diff --git a/src/lib.rs b/src/lib.rs
index 36300ca..8b114c2 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -31,6 +31,14 @@ pub struct Zephyr {
 /// Value -> Rules
 pub type SpecialRule = Box<dyn Fn(&str) -> String>;
 
+#[derive(PartialEq, Debug)]
+pub enum ZephyrError {
+    /// the provided rule has invalid braces (single braces, or in incorrect order `..}...{..`)
+    InvalidBraces,
+    /// the provided rule isn't a no-variable rule, but no variables were provided
+    ValueMissing,
+}
+
 impl Zephyr {
     /// builds a `Zephyr` with the default ruleset
     pub fn new() -> Self {
@@ -80,15 +88,15 @@ impl Zephyr {
                 }
             })
             // we ignore errors
-            .flat_map(|c| self.generate_class(c).ok().flatten())
+            .flat_map(|c| self.generate_class(c).ok())
             .collect::<Vec<_>>()
             .join("")
     }
 
     /// this one returns an error if parsing or generating fails
-    // TODO add an error type
-    pub fn generate_class(&self, class: &str) -> Result<Option<String>, &'static str> {
-        parse_class(class).map(|c| c.generate(self)).transpose()
+    pub fn generate_class(&self, class: &str) -> Result<String, ZephyrError> {
+        let c = parse_class(class)?;
+        c.generate(self)
     }
 }
 
diff --git a/src/parse.rs b/src/parse.rs
index 2012905..5145709 100644
--- a/src/parse.rs
+++ b/src/parse.rs
@@ -1,7 +1,6 @@
-use crate::class::Class;
+use crate::{class::Class, ZephyrError};
 
-// TODO return error
-pub(crate) fn parse_class<'a>(original: &'a str) -> Option<Class<'a>> {
+pub(crate) fn parse_class<'a>(original: &'a str) -> Result<Class<'a>, ZephyrError> {
     // this code is kinda repetitive but idk
 
     let (class, pseudo) = if let Some((class, pseudo)) = original.split_once('$') {
@@ -17,7 +16,7 @@ pub(crate) fn parse_class<'a>(original: &'a str) -> Option<Class<'a>> {
             class[p + 1..].split(',').collect()
         };
 
-        return Some(Class {
+        return Ok(Class {
             name: &class[0..p],
             value: None,
             modifiers: mods.into(),
@@ -35,7 +34,7 @@ pub(crate) fn parse_class<'a>(original: &'a str) -> Option<Class<'a>> {
                 class[end + 1..].split(',').collect()
             };
 
-            return Some(Class {
+            return Ok(Class {
                 name: &class[0..start],
                 value: Some(&class[start + 1..end]),
                 modifiers: mods.into(),
@@ -46,9 +45,9 @@ pub(crate) fn parse_class<'a>(original: &'a str) -> Option<Class<'a>> {
         }
         // go to [...] case
         (None, None) => {}
+        // braces do not form a valid block
         _ => {
-            // TODO return an error here
-            return None;
+            return Err(ZephyrError::InvalidBraces);
         }
     };
 
@@ -60,7 +59,7 @@ pub(crate) fn parse_class<'a>(original: &'a str) -> Option<Class<'a>> {
                 class[end + 1..].split(',').collect()
             };
 
-            return Some(Class {
+            return Ok(Class {
                 name: &class[0..start],
                 value: Some(&class[start + 1..end]),
                 modifiers: mods.into(),
@@ -70,7 +69,7 @@ pub(crate) fn parse_class<'a>(original: &'a str) -> Option<Class<'a>> {
             });
         }
         _ => {
-            return Some(Class {
+            return Ok(Class {
                 name: &class[0..],
                 value: None,
                 modifiers: vec![].into(),
@@ -96,7 +95,7 @@ mod tests {
     ) {
         assert_eq!(
             parse_class(class),
-            Some(Class {
+            Ok(Class {
                 name,
                 value,
                 modifiers: modifiers.into(),
@@ -112,7 +111,7 @@ mod tests {
     ) {
         assert_eq!(
             parse_class(class),
-            Some(Class {
+            Ok(Class {
                 name,
                 value,
                 modifiers: modifiers.into(),