diff --git a/src/lib.rs b/src/lib.rs
index 9c6d907..6445fe6 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,6 +1,7 @@
 //! hinoirisetr library
 //! Contains core logic for computing temperature and gamma and applying settings.
 
+use std::collections::HashSet;
 use std::fs::File;
 use std::io::{BufRead, BufReader};
 use std::path::Path;
@@ -80,6 +81,7 @@ pub enum ConfigError {
     InvalidGamma(String),
     InvalidGammaBackend(String),
     InvalidTempBackend(String),
+    DuplicateKey(String),
 }
 
 impl From<std::io::Error> for ConfigError {
@@ -99,6 +101,8 @@ impl Config {
         trace!("Config::load({path:?})");
         let mut config = Self::default(); // Start with default values
 
+        let mut seen_keys = HashSet::new();
+
         let config_file = File::open(path)?;
         let reader = BufReader::new(config_file);
         let mut current_section = String::new();
@@ -113,12 +117,21 @@ impl Config {
             trace!("line: {line}");
             if line.starts_with('[') && line.contains(']') {
                 current_section = line[1..line.find(']').unwrap()].to_string();
+                seen_keys.clear();
                 trace!("current_section: {current_section}");
             } else if let Some((key, value)) = line.split_once('=') {
                 trace!("key: {key}, value: {value}");
                 let key_trimmed_string = key.trim().replace('"', "");
                 let key_trimmed = key_trimmed_string.as_str();
 
+                // Check for duplicate key in current section
+                if seen_keys.contains(key_trimmed) {
+                    return Err(ConfigError::DuplicateKey(format!(
+                        "Duplicate key '{key_trimmed}' in section '{current_section}'",
+                    )));
+                }
+                seen_keys.insert(key_trimmed.to_string());
+
                 let value = value.trim().replace('"', "");
                 match current_section.as_str() {
                     "" => match key_trimmed {
@@ -236,6 +249,8 @@ impl Config {
             )));
         }
 
+        debug!("Seen: {:#?}", seen_keys);
+
         Ok(config)
     }
 }