diff --git a/implementations/rust/preserves/src/hex.rs b/implementations/rust/preserves/src/hex.rs
index 7adb7cf..14fd09b 100644
--- a/implementations/rust/preserves/src/hex.rs
+++ b/implementations/rust/preserves/src/hex.rs
@@ -36,7 +36,11 @@ impl HexParser {
                     },
             }
         }
-        Some(result)
+        if buf_full {
+            None // odd number of hexits
+        } else {
+            Some(result)
+        }
     }
 }