diff --git a/src/fast_api.rs b/src/fast_api.rs
index db76fb69..3611c360 100644
--- a/src/fast_api.rs
+++ b/src/fast_api.rs
@@ -218,14 +218,9 @@ pub struct FastApiOneByteString {
 
 impl FastApiOneByteString {
   #[inline(always)]
-  pub fn as_str(&self) -> &str {
-    // SAFETY: The string is guaranteed to be valid UTF-8.
-    unsafe {
-      std::str::from_utf8_unchecked(std::slice::from_raw_parts(
-        self.data,
-        self.length as usize,
-      ))
-    }
+  pub fn as_bytes(&self) -> &[u8] {
+    // SAFETY: The data is guaranteed to be valid for the length of the string.
+    unsafe { std::slice::from_raw_parts(self.data, self.length as usize) }
   }
 }
 
diff --git a/tests/test_api.rs b/tests/test_api.rs
index dea0bf27..d95ffd97 100644
--- a/tests/test_api.rs
+++ b/tests/test_api.rs
@@ -8915,8 +8915,8 @@ fn test_fast_calls_onebytestring() {
     data: *const fast_api::FastApiOneByteString,
   ) -> u32 {
     unsafe { WHO = "fast" };
-    let data = unsafe { &*data }.as_str();
-    assert_eq!("hello", data);
+    let data = unsafe { &*data }.as_bytes();
+    assert_eq!(b"hello", data);
     data.len() as u32
   }