diff --git a/src/multi_array_operation.cc b/src/multi_array_operation.cc
index 0e30e72..d8f8525 100644
--- a/src/multi_array_operation.cc
+++ b/src/multi_array_operation.cc
@@ -54,6 +54,7 @@ namespace MultiArrayTools
     template <typename T>
     std::shared_ptr<BlockBase<T> > makeBlock(const std::vector<T>& vec, size_t stepSize, size_t blockSize)
     {
+	VCHECK(stepSize);
 	if(stepSize == 0){
 	    return std::make_shared<BlockValue<T> >(vec, 0, blockSize);
 	}
@@ -68,6 +69,7 @@ namespace MultiArrayTools
     template <typename T>
     std::shared_ptr<MutableBlockBase<T> > makeBlock(std::vector<T>& vec, size_t stepSize, size_t blockSize)
     {
+	VCHECK(stepSize);
 	if(stepSize == 0){
 	    return std::make_shared<MBlockValue<T> >(vec, 0, blockSize);
 	}
diff --git a/src/op_unit_test.cc b/src/op_unit_test.cc
index 2f2e797..d743049 100644
--- a/src/op_unit_test.cc
+++ b/src/op_unit_test.cc
@@ -110,7 +110,7 @@ namespace {
 	EXPECT_EQ( fabs( res.at('f') - (0.373+8.215) ) < 0.0001, true );
 	EXPECT_EQ( fabs( res.at('g') - (7.192+5.063) ) < 0.0001, true );
     }
-    /*
+
     TEST_F(OpTest_MDim, ExecOp1)
     {
 	MultiArray<double,SRange,SRange> res(sr2ptr,sr4ptr);
@@ -132,7 +132,7 @@ namespace {
 	EXPECT_EQ( fabs( res.at(mkt('3','B')) - (0.373 * 4.790) ) < 0.0001, true );
 
     }
-
+    /*
     TEST_F(OpTest_MDim, ExecOp2)
     {
 	MultiArray<double,MRange,SRange> res(mr1ptr,sr4ptr);