diff --git a/src/ser.rs b/src/ser.rs
index 80c2deb0c..b38f3486b 100644
--- a/src/ser.rs
+++ b/src/ser.rs
@@ -2064,6 +2064,8 @@ static ESCAPE: [u8; 256] = [
 
 /// Serialize the given data structure as JSON into the IO stream.
 ///
+/// Serialization guarantees it only feeds valid UTF-8 sequences to the writer.
+///
 /// # Errors
 ///
 /// Serialization can fail if `T`'s implementation of `Serialize` decides to
@@ -2082,6 +2084,8 @@ where
 /// Serialize the given data structure as pretty-printed JSON into the IO
 /// stream.
 ///
+/// Serialization guarantees it only feeds valid UTF-8 sequences to the writer.
+///
 /// # Errors
 ///
 /// Serialization can fail if `T`'s implementation of `Serialize` decides to