diff --git a/compiler/rustc_metadata/src/rmeta/encoder.rs b/compiler/rustc_metadata/src/rmeta/encoder.rs
index be91ad4088a..5ade67c62ff 100644
--- a/compiler/rustc_metadata/src/rmeta/encoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/encoder.rs
@@ -347,6 +347,13 @@ fn encode(&self, s: &mut EncodeContext<'a, 'tcx>) {
     }
 }
 
+impl<'a, 'tcx> Encodable<EncodeContext<'a, 'tcx>> for [u8] {
+    fn encode(&self, e: &mut EncodeContext<'a, 'tcx>) {
+        Encoder::emit_usize(e, self.len());
+        e.emit_raw_bytes(self);
+    }
+}
+
 impl<'a, 'tcx> TyEncoder for EncodeContext<'a, 'tcx> {
     const CLEAR_CROSS_CRATE: bool = true;