Index: test/containers/MoveOnly.h
===================================================================
--- test/containers/MoveOnly.h
+++ test/containers/MoveOnly.h
@@ -22,11 +22,17 @@
 
     int data_;
 public:
-    MoveOnly(int data = 1) : data_(data) {}
-    MoveOnly(MoveOnly&& x)
-        : data_(x.data_) {x.data_ = 0;}
-    MoveOnly& operator=(MoveOnly&& x)
-        {data_ = x.data_; x.data_ = 0; return *this;}
+    MoveOnly(int data = 0) : data_(data) { assert(data != -1); }
+    MoveOnly(MoveOnly &&x) : data_(x.data_) {
+        assert(x.data_ != -1);
+        x.data_ = -1;
+    }
+    MoveOnly &operator=(MoveOnly &&x) {
+        assert(x.data_ != -1);
+        data_ = x.data_;
+        x.data_ = -1;
+        return *this;
+    }
 
     int get() const {return data_;}