diff --git a/README.md b/README.md
index 7a24554..0985cec 100644
--- a/README.md
+++ b/README.md
@@ -31,4 +31,12 @@ Setting a theme (default is an [included xcode-like theme](qlhighlight/res/Xcode
 
 Available themes are the default theme and [these](https://docs.rs/syntect/2.0.0/syntect/highlighting/struct.ThemeSet.html#method.load_defaults).
 
+Adding additional themes. Set to absolute path of directory containing `.tmTheme` files:
+
+    defaults write de.bastianrinsche.QLSyntaxHighlight themeDirectory '/path/to/themes'
+    
+Adding addiontal syntaxes. Set to absolute path of directory containing `.sublime-syntax` files:
+
+    defaults write de.bastianrinsche.QLSyntaxHighlight syntaxDirectory '/path/to/syntaxes'
+
 ![screenshot](img/screenshot.png)
diff --git a/qlhighlight/src/lib.rs b/qlhighlight/src/lib.rs
index 7f6e783..c28a0c4 100644
--- a/qlhighlight/src/lib.rs
+++ b/qlhighlight/src/lib.rs
@@ -6,6 +6,7 @@ mod quicklook;
 
 use std::fmt::Write;
 use std::io::Cursor;
+use std::path::Path;
 
 use core_foundation::base::{OSStatus, TCFType};
 use core_foundation::data::CFData;
@@ -36,9 +37,30 @@ pub extern "C" fn GeneratePreviewForURL(
     let theme_bytes = include_bytes!("../res/XCodelike.tmTheme");
     let xcode_theme = ThemeSet::load_from_reader(&mut Cursor::new(&theme_bytes[..])).unwrap();
 
-    let ts = ThemeSet::load_defaults();
-    let syntax_set = SyntaxSet::load_defaults_nonewlines();
-    let theme = ts.themes
+    let mut theme_set = ThemeSet::load_defaults();
+    let mut syntax_set = SyntaxSet::load_defaults_nonewlines();
+
+    if let Some(theme_dir) = conf.theme_dir {
+        let directory = theme_dir.to_string();
+        let theme_dir = Path::new(&directory);
+        if let Ok(mut custom_themes) = ThemeSet::load_from_folder(&theme_dir) {
+            theme_set.themes.append(&mut custom_themes.themes);
+        }
+    };
+
+    if let Some(syntax_dir) = conf.syntax_dir {
+        let directory = syntax_dir.to_string();
+        let syntax_dir = Path::new(&directory);
+        if let Ok(mut custom_syntaxes) = SyntaxSet::load_from_folder(&syntax_dir) {
+            for set in custom_syntaxes.syntaxes() {
+                syntax_set.add_syntax(set.clone());
+            }
+            syntax_set.link_syntaxes()
+        }
+    };
+
+    let theme = theme_set
+        .themes
         .get(&conf.theme_name.to_string())
         .unwrap_or(&xcode_theme);
 
diff --git a/qlhighlight/src/quicklook.rs b/qlhighlight/src/quicklook.rs
index f57571a..0aa0f65 100644
--- a/qlhighlight/src/quicklook.rs
+++ b/qlhighlight/src/quicklook.rs
@@ -3,6 +3,7 @@ use core_foundation::data::CFDataRef;
 use core_foundation::string::CFStringRef;
 use core_foundation::dictionary::CFDictionaryRef;
 
+#[allow(dead_code)]
 extern "C" {
     #[link_name = "kUTTypeHTML"]
     pub static kUTTypeHTML: CFStringRef;
diff --git a/qlhighlight/src/util.rs b/qlhighlight/src/util.rs
index 1ee9ed7..c47db97 100644
--- a/qlhighlight/src/util.rs
+++ b/qlhighlight/src/util.rs
@@ -17,18 +17,28 @@ extern "C" {
     pub static kCFPreferencesAnyHost: CFStringRef;
 }
 
+const FONT_SIZE: &'static str = "fontSize";
+const FONT_FAMILY: &'static str = "fontFamily";
+const THEME: &'static str = "theme";
+const THEME_DIR: &'static str = "themeDirectory";
+const SYNTAX_DIR: &'static str = "syntaxDirectory";
+
 #[derive(Debug)]
 pub struct Config {
     pub font_size: CFString,
     pub font_family: CFString,
     pub theme_name: CFString,
+    pub theme_dir: Option<CFString>,
+    pub syntax_dir: Option<CFString>,
 }
 
 pub fn get_settings() -> Config {
     let keys = CFArray::from_CFTypes(&[
-        CFString::new("fontSize"),
-        CFString::new("fontFamily"),
-        CFString::new("theme"),
+        CFString::new(FONT_SIZE),
+        CFString::new(FONT_FAMILY),
+        CFString::new(THEME),
+        CFString::new(THEME_DIR),
+        CFString::new(SYNTAX_DIR),
     ]);
 
     let prefs = unsafe {
@@ -43,23 +53,33 @@ pub fn get_settings() -> Config {
     let prefs: CFDictionary = unsafe { CFDictionary::wrap_under_get_rule(prefs) };
 
     let font_size = prefs
-        .find2(&CFString::new("fontSize"))
+        .find2(&CFString::new(FONT_SIZE))
         .and_then(|ptr| unsafe { CFType::wrap_under_create_rule(ptr).downcast::<CFString>() })
         .unwrap_or(CFString::new("11"));
 
     let font_family = prefs
-        .find2(&CFString::new("fontFamily"))
+        .find2(&CFString::new(FONT_FAMILY))
         .and_then(|ptr| unsafe { CFType::wrap_under_create_rule(ptr).downcast::<CFString>() })
         .unwrap_or(CFString::new("Menlo, monospace"));
 
     let theme_name = prefs
-        .find2(&CFString::new("theme"))
+        .find2(&CFString::new(THEME))
         .and_then(|ptr| unsafe { CFType::wrap_under_create_rule(ptr).downcast::<CFString>() })
         .unwrap_or(CFString::new("InspiredGithub"));
 
+    let theme_dir = prefs
+        .find2(&CFString::new(THEME_DIR))
+        .and_then(|ptr| unsafe { CFType::wrap_under_create_rule(ptr).downcast::<CFString>() });
+
+    let syntax_dir = prefs
+        .find2(&CFString::new(SYNTAX_DIR))
+        .and_then(|ptr| unsafe { CFType::wrap_under_create_rule(ptr).downcast::<CFString>() });
+
     Config {
         font_size,
         font_family,
         theme_name,
+        theme_dir,
+        syntax_dir,
     }
 }