diff --git a/lesson4_invariants/simple_voting/Voting.conf b/lesson4_invariants/simple_voting/Voting.conf
index 72d760d..408e872 100644
--- a/lesson4_invariants/simple_voting/Voting.conf
+++ b/lesson4_invariants/simple_voting/Voting.conf
@@ -1,9 +1,14 @@
 {
     "files": [
-        "Voting.sol:Voting"
+        "Voting.sol"
     ],
     "verify": "Voting:Voting.spec",
     "wait_for_results": "all",
     "rule_sanity": "basic",
-    "msg": "A simple invariant example"
+    "msg": "A simple invariant example",
+    "mutations": {
+        "gambit": {
+            "filename": "Voting.sol"
+        }
+    }
 }
diff --git a/lesson4_invariants/simple_voting/mutate.mconf b/lesson4_invariants/simple_voting/mutate.mconf
deleted file mode 100644
index 7114cc2..0000000
--- a/lesson4_invariants/simple_voting/mutate.mconf
+++ /dev/null
@@ -1,5 +0,0 @@
-{
-    "gambit": {
-        "filename": "Voting.sol"
-    }
-}