diff --git a/unsupported/Eigen/CXX11/src/Tensor/TensorExecutor.h b/unsupported/Eigen/CXX11/src/Tensor/TensorExecutor.h
index ad5c97b57..9075fb3fa 100644
--- a/unsupported/Eigen/CXX11/src/Tensor/TensorExecutor.h
+++ b/unsupported/Eigen/CXX11/src/Tensor/TensorExecutor.h
@@ -159,7 +159,9 @@ class TensorExecutor<Expression, ThreadPoolDevice, Vectorizable> {
 #else
       size_t num_threads = device.numThreads();
       if (num_threads > 1) {
-        cost = evaluator.costPerCoeff(Vectorizable)
+        // FIXME: the following line is broken (see bug 1255),
+        //        but maybe the cost should be used somewhere to drive the execution.
+        //cost = evaluator.costPerCoeff(Vectorizable)
         num_threads = TensorCostModel<ThreadPoolDevice>::numThreads(
             size, evaluator.costPerCoeff(Vectorizable), num_threads);
       }