diff --git a/.travis.yml b/.travis.yml
index ceea27b..7d64403 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,9 +1,14 @@
 language: rust
 sudo: false
+rust:
+  - stable
+  - beta
+  - nightly
+
 matrix:
-  include:
-    - rust: 1.32.0
-    - rust: stable
+  allow_failures:
+    - rust: nightly
+
 branches:
   only:
     - master
diff --git a/src/lib.rs b/src/lib.rs
index aaa9d25..48d828b 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -112,7 +112,7 @@ mod tests {
         let extended_mac = super::WolPacket::extend_mac(&mac);
 
         assert_eq!(extended_mac.len(), super::MAC_PER_MAGIC * super::MAC_SIZE);
-        assert_eq!(&extended_mac[90..], &mac[..]);
+        assert_eq!(&extended_mac[(super::MAC_PER_MAGIC - 1) * super::MAC_SIZE..], &mac[..]);
     }
 
     #[test]