diff --git a/src/deno_dir.rs b/src/deno_dir.rs
index 09f37933bc..1a8c929acc 100644
--- a/src/deno_dir.rs
+++ b/src/deno_dir.rs
@@ -70,7 +70,7 @@ impl DenoDir {
   ) -> std::io::Result<String> {
     let path = self.cache_path(filename, source_code);
     debug!("load_cache {}", path.display());
-    fs::read_file_sync(&path)
+    fs::read_file_sync_string(&path)
   }
 
   pub fn code_cache(
@@ -251,7 +251,7 @@ fn test_code_cache() {
   let r = deno_dir.code_cache(filename, source_code, output_code);
   r.expect("code_cache error");
   assert!(cache_path.exists());
-  assert_eq!(output_code, fs::read_file_sync(&cache_path).unwrap());
+  assert_eq!(output_code, fs::read_file_sync_string(&cache_path).unwrap());
 }
 
 // https://github.com/denoland/deno/blob/golang/deno_dir.go#L25-L30
@@ -413,6 +413,6 @@ fn get_source_code(
       module_name == filename,
       "if a module isn't remote, it should have the same filename"
     );
-    fs::read_file_sync(Path::new(filename))
+    fs::read_file_sync_string(Path::new(filename))
   }
 }
diff --git a/src/fs.rs b/src/fs.rs
index 4ec9611aea..0aaf2a93d2 100644
--- a/src/fs.rs
+++ b/src/fs.rs
@@ -3,15 +3,20 @@ use std::fs::File;
 use std::io::Read;
 use std::path::Path;
 
-#[allow(dead_code)]
-pub fn read_file_sync(path: &Path) -> std::io::Result<String> {
+pub fn read_file_sync(path: &Path) -> std::io::Result<Vec<u8>> {
   File::open(path).and_then(|mut f| {
-    let mut contents = String::new();
-    f.read_to_string(&mut contents)?;
-    Ok(contents)
+    let mut buffer = Vec::new();
+    f.read_to_end(&mut buffer)?;
+    Ok(buffer)
   })
 }
 
+pub fn read_file_sync_string(path: &Path) -> std::io::Result<String> {
+  let vec = read_file_sync(path)?;
+  String::from_utf8(vec)
+    .map_err(|err| std::io::Error::new(std::io::ErrorKind::InvalidData, err))
+}
+
 pub fn mkdir(path: &Path) -> std::io::Result<()> {
   debug!("mkdir -p {}", path.display());
   assert!(path.has_root(), "non-has_root not yet implemented");