diff --git a/Rakefile b/Rakefile
index b25c822..2542d9d 100644
--- a/Rakefile
+++ b/Rakefile
@@ -69,17 +69,17 @@ task :init_mspec do |_t|
 end
 
 task test: [:cargo, :minitest, :lint, :pbench, :init_mspec] do |_t|
-  exec 'spec/mspec/bin/mspec --format spec core/file/basename core/file/extname core/file/dirname library/pathname'
+  exec 'bundle exec spec/mspec/bin/mspec --format spec core/file/basename core/file/extname core/file/dirname library/pathname'
 end
 
 desc "Full mspec results w/o encoding"
 task mspec_full: :init_mspec do
-  exec %(bash -c "TEST_MONKEYPATCHES=true WITH_REGRESSION=true spec/mspec/bin/mspec --format spec core/file/basename core/file/extname core/file/dirname library/pathname")
+  exec %(bash -c "TEST_MONKEYPATCHES=true WITH_REGRESSION=true bundle exec spec/mspec/bin/mspec --format spec core/file/basename core/file/extname core/file/dirname library/pathname")
 end
 
 desc "Full mspec results w/ encoding"
 task mspec_encoding_full: :init_mspec do
-  exec %(bash -c "ENCODING=1 TEST_MONKEYPATCHES=true WITH_REGRESSION=true mspec --format spec core/file/basename core/file/extname core/file/dirname library/pathname")
+  exec %(bash -c "ENCODING=1 TEST_MONKEYPATCHES=true WITH_REGRESSION=true bundle exec spec/mspec/bin/mspec --format spec core/file/basename core/file/extname core/file/dirname library/pathname")
 end
 
 Rake::TestTask.new(bench: :build_lib) do |t|
diff --git a/src/basename.rs b/src/basename.rs
index a663e52..6c03b0e 100644
--- a/src/basename.rs
+++ b/src/basename.rs
@@ -4,25 +4,24 @@ use self::memchr::memrchr;
 
 use path_parsing::{find_last_sep_pos, find_last_non_sep_pos};
 
-pub fn basename<'a>(path: &'a str, ext: &str) -> &'a str {
-  let bytes: &[u8] = path.as_bytes();
+pub fn basename<'a>(path: &'a [u8], ext: &str) -> &'a [u8] {
   let mut left: usize = 0;
-  let mut right: usize = bytes.len();
-  if let Some(last_slash_pos) = find_last_sep_pos(bytes) {
+  let mut right: usize = path.len();
+  if let Some(last_slash_pos) = find_last_sep_pos(path) {
     if last_slash_pos == right - 1 {
-      if let Some(pos) = find_last_non_sep_pos(&bytes[..last_slash_pos]) {
+      if let Some(pos) = find_last_non_sep_pos(&path[..last_slash_pos]) {
         right = pos + 1;
       } else {
-        return "/";
+        return "/".as_bytes();
       }
-      if let Some(pos) = find_last_sep_pos(&bytes[..right]) {
+      if let Some(pos) = find_last_sep_pos(&path[..right]) {
         left = pos + 1;
       }
     } else {
       left = last_slash_pos + 1;
     }
   }
-  &path[left..left + ext_end(&bytes[left..right], ext)]
+  &path[left..left + ext_end(&path[left..right], ext)]
 }
 
 fn ext_end(slice: &[u8], ext: &str) -> usize {
@@ -44,103 +43,103 @@ fn ext_end(slice: &[u8], ext: &str) -> usize {
 #[test]
 fn non_dot_asterisk_ext() {
   // This is undocumented Ruby functionality. We match it in case some code out there relies on it.
-  assert_eq!(basename("abc", "b*"), "a");
-  assert_eq!(basename("abc", "abc"), "abc");
-  assert_eq!(basename("abc", "a*"), "abc");
-  assert_eq!(basename("playlist", "l*"), "play");
+  assert_eq!(basename("abc".as_bytes(), "b*"), b"a");
+  assert_eq!(basename("abc".as_bytes(), "abc"), b"abc");
+  assert_eq!(basename("abc".as_bytes(), "a*"), b"abc");
+  assert_eq!(basename("playlist".as_bytes(), "l*"), b"play");
   // Treated as literal "*":
-  assert_eq!(basename("playlist", "yl*"), "playlist");
-  assert_eq!(basename("playl*", "yl*"), "pla");
+  assert_eq!(basename("playlist".as_bytes(), "yl*"), b"playlist");
+  assert_eq!(basename("playl*".as_bytes(), "yl*"), b"pla");
 }
 
 #[test]
 fn empty() {
-  assert_eq!(basename("", ""), "");
-  assert_eq!(basename("", ".*"), "");
-  assert_eq!(basename("", ".a"), "");
+  assert_eq!(basename("".as_bytes(), ""), b"");
+  assert_eq!(basename("".as_bytes(), ".*"), b"");
+  assert_eq!(basename("".as_bytes(), ".a"), b"");
 }
 
 #[test]
 fn sep() {
-  assert_eq!(basename("/", ""), "/");
-  assert_eq!(basename("//", ""), "/");
+  assert_eq!(basename("/".as_bytes(), ""), b"/");
+  assert_eq!(basename("//".as_bytes(), ""), b"/");
 }
 
 #[test]
 fn trailing_dot() {
-  assert_eq!(basename("file.test.", ""), "file.test.");
-  assert_eq!(basename("file.test.", "."), "file.test");
-  assert_eq!(basename("file.test.", ".*"), "file.test");
+  assert_eq!(basename("file.test.".as_bytes(), ""), b"file.test.");
+  assert_eq!(basename("file.test.".as_bytes(), "."), b"file.test");
+  assert_eq!(basename("file.test.".as_bytes(), ".*"), b"file.test");
 }
 
 #[test]
 fn trailing_dot_dot() {
-  assert_eq!(basename("a..", ".."), "a");
-  assert_eq!(basename("a..", ".*"), "a.");
+  assert_eq!(basename("a..".as_bytes(), ".."), b"a");
+  assert_eq!(basename("a..".as_bytes(), ".*"), b"a.");
 }
 
 #[test]
 fn dot() {
-  assert_eq!(basename(".", ""), ".");
-  assert_eq!(basename(".", "."), ".");
-  assert_eq!(basename(".", ".*"), ".");
+  assert_eq!(basename(".".as_bytes(), ""), b".");
+  assert_eq!(basename(".".as_bytes(), "."), b".");
+  assert_eq!(basename(".".as_bytes(), ".*"), b".");
 }
 
 #[test]
 fn dot_dot() {
-  assert_eq!(basename("..", ""), "..");
-  assert_eq!(basename("..", ".*"), "..");
-  assert_eq!(basename("..", ".."), "..");
-  assert_eq!(basename("..", "..."), "..");
+  assert_eq!(basename("..".as_bytes(), ""), b"..");
+  assert_eq!(basename("..".as_bytes(), ".*"), b"..");
+  assert_eq!(basename("..".as_bytes(), ".."), b"..");
+  assert_eq!(basename("..".as_bytes(), "..."), b"..");
 }
 
 #[test]
 fn non_dot_ext() {
-  assert_eq!(basename("abc", "bc"), "a");
+  assert_eq!(basename("abc".as_bytes(), "bc"), b"a");
 }
 
 #[test]
 fn basename_eq_ext() {
-  assert_eq!(basename(".x", ".x"), ".x");
-  assert_eq!(basename(".x", ".*"), ".x");
+  assert_eq!(basename(".x".as_bytes(), ".x"), b".x");
+  assert_eq!(basename(".x".as_bytes(), ".*"), b".x");
 }
 
 #[test]
 fn absolute() {
-  assert_eq!(basename("/a/b///c", ""), "c");
+  assert_eq!(basename("/a/b///c".as_bytes(), ""), b"c");
 }
 
 #[test]
 fn trailing_slashes_absolute() {
-  assert_eq!(basename("/a/b///c//////", ""), "c");
+  assert_eq!(basename("/a/b///c//////".as_bytes(), ""), b"c");
 }
 
 #[test]
 fn relative() {
-  assert_eq!(basename("b///c", ""), "c");
+  assert_eq!(basename("b///c".as_bytes(), ""), b"c");
 }
 
 #[test]
 fn trailing_slashes_relative() {
-  assert_eq!(basename("b/c//", ""), "c");
+  assert_eq!(basename("b/c//".as_bytes(), ""), b"c");
 }
 
 #[test]
 fn root() {
-  assert_eq!(basename("//c", ""), "c");
+  assert_eq!(basename("//c".as_bytes(), ""), b"c");
 }
 
 #[test]
 fn trailing_slashes_root() {
-  assert_eq!(basename("//c//", ""), "c");
+  assert_eq!(basename("//c//".as_bytes(), ""), b"c");
 }
 
 #[test]
 fn trailing_slashes_relative_root() {
-  assert_eq!(basename("c//", ""), "c");
+  assert_eq!(basename("c//".as_bytes(), ""), b"c");
 }
 
 #[test]
 fn edge_case_all_seps() {
-  assert_eq!("/", basename("///", ".*"));
+  assert_eq!(b"/", basename("///".as_bytes(), ".*"));
 }
diff --git a/src/cleanpath_aggressive.rs b/src/cleanpath_aggressive.rs
index d976301..7628883 100644
--- a/src/cleanpath_aggressive.rs
+++ b/src/cleanpath_aggressive.rs
@@ -27,7 +27,7 @@ pub fn cleanpath_aggressive(path: &str) -> Cow<str> {
   // pre.tr!(File::ALT_SEPARATOR, File::SEPARATOR) if File::ALT_SEPARATOR
   // ```
   //
-  if contains_sep(basename(&prefix, "").as_bytes()) {
+  if contains_sep(basename(&prefix.as_bytes(), "")) {
     let len = names.iter().rposition(|&c| c != "..").map_or(0, |pos| pos + 1);
     names.truncate(len);
   }
diff --git a/src/cleanpath_conservative.rs b/src/cleanpath_conservative.rs
index f4c7b87..9e48e6c 100644
--- a/src/cleanpath_conservative.rs
+++ b/src/cleanpath_conservative.rs
@@ -21,7 +21,7 @@ pub fn cleanpath_conservative(path: &str) -> Cow<str> {
   // pre.tr!(File::ALT_SEPARATOR, File::SEPARATOR) if File::ALT_SEPARATOR
   // ```
   //
-  if contains_sep(basename(&prefix, "").as_bytes()) {
+  if contains_sep(basename(&prefix.as_bytes(), "")) {
     let len = names.iter().rposition(|&c| c != "..").map_or(0, |pos| pos + 1);
     names.truncate(len);
   }
@@ -31,7 +31,7 @@ pub fn cleanpath_conservative(path: &str) -> Cow<str> {
     None => return dirname(&prefix).into(),
   };
 
-  if last_name != ".." && basename(&path, "") == "." {
+  if last_name != ".." && basename(&path.as_bytes(), "") == ".".as_bytes() {
     names.reverse();
     names.push(".");
   } else if last_name != "." && last_name != ".." &&
diff --git a/src/helpers.rs b/src/helpers.rs
index e360eb3..115c9e8 100644
--- a/src/helpers.rs
+++ b/src/helpers.rs
@@ -44,7 +44,14 @@ pub fn anyobject_to_string(item: AnyObject) -> Result<String, RubyDebugInfo> {
 
 pub fn to_str(maybe_string: &MaybeString) -> &str {
   match maybe_string {
-    &Ok(ref rutie_string) => rutie_string.to_str(),
+    &Ok(ref rutie_string) => rutie_string.to_str_unchecked(),
     &Err(_) => "",
   }
 }
+
+pub fn to_bytes(maybe_string: &MaybeString) -> &[u8] {
+  match maybe_string {
+    &Ok(ref rutie_string) => rutie_string.to_bytes_unchecked(),
+    &Err(_) => &[],
+  }
+}
diff --git a/src/pathname.rs b/src/pathname.rs
index b419500..bc29a96 100644
--- a/src/pathname.rs
+++ b/src/pathname.rs
@@ -8,7 +8,7 @@ use extname;
 use plus;
 use relative_path_from;
 use debug;
-use helpers::{TryFrom, to_str};
+use helpers::{TryFrom, to_str, to_bytes};
 use path_parsing::{SEP, find_last_non_sep_pos};
 
 use rutie;
@@ -23,6 +23,7 @@ use rutie::{
   VerifiedObject,
   Exception as Exc,
   AnyException as Exception,
+  Encoding,
 };
 use rutie::types::{Value, ValueType};
 use std::borrow::Cow;
@@ -105,7 +106,7 @@ pub fn pn_is_absolute(pth: MaybeString) -> Boolean {
 // pub fn pn_ascend(){}
 
 pub fn pn_basename(pth: MaybeString, ext: MaybeString) -> RString {
-  RString::new_utf8(basename::basename(to_str(&pth), to_str(&ext)))
+  RString::from_bytes(basename::basename(to_bytes(&pth), to_str(&ext)), &Encoding::utf8())
 }
 
 pub fn pn_children(pth: MaybeString, with_dir: MaybeBoolean) -> Result<AnyObject, Exception> {