diff --git a/implementations/rust/preserves/src/value/text/writer.rs b/implementations/rust/preserves/src/value/text/writer.rs
index 401889d..edb938b 100644
--- a/implementations/rust/preserves/src/value/text/writer.rs
+++ b/implementations/rust/preserves/src/value/text/writer.rs
@@ -37,13 +37,13 @@ impl TextWriter<&mut Vec<u8>> {
     pub fn encode<D: Embeddable, N: NestedValue<D>, Enc: DomainEncode<D>>(
         enc: &mut Enc,
         v: &N,
-    ) -> io::Result<Vec<u8>> {
+    ) -> io::Result<String> {
         let mut buf: Vec<u8> = Vec::new();
         TextWriter::new(&mut buf).write(enc, v)?;
-        Ok(buf)
+        Ok(String::from_utf8(buf).expect("valid UTF-8 from TextWriter"))
     }
 
-    pub fn encode_iovalue(v: &IOValue) -> io::Result<Vec<u8>> {
+    pub fn encode_iovalue(v: &IOValue) -> io::Result<String> {
         Self::encode(&mut IOValueDomainCodec, v)
     }
 }