diff --git a/src/libserialize/json.rs b/src/libserialize/json.rs
index d42132440163c..ed2e6167cbb05 100644
--- a/src/libserialize/json.rs
+++ b/src/libserialize/json.rs
@@ -365,6 +365,9 @@ impl std::error::Error for EncoderError {
 }
 
 impl From<fmt::Error> for EncoderError {
+    /// Converts a [`fmt::Error`] into `EncoderError`
+    ///
+    /// This conversion does not allocate memory.
     fn from(err: fmt::Error) -> EncoderError { EncoderError::FmtError(err) }
 }