diff --git a/cnorxz/core/include/array_wrapper.h b/cnorxz/core/include/array_wrapper.h
index ca8745f..58052df 100644
--- a/cnorxz/core/include/array_wrapper.h
+++ b/cnorxz/core/include/array_wrapper.h
@@ -24,7 +24,7 @@ namespace CNORXZ
 	virtual void readFile(cer::Format f, const String& fname) const = 0;
 #endif
 	virtual int typenum() const = 0;
-	virtual const void* data() const = 0;
+	virtual void* data() const = 0;
 	virtual SizeT datasize() const = 0;
     };
 
@@ -92,8 +92,8 @@ namespace CNORXZ
 	}
 #endif
 	virtual int typenum() const override final { return Typenum<T>::value; }
-	virtual const void* data() const override final
-	{ return reinterpret_cast<const void*>( mArr->data() ); }
+	virtual void* data() const override final
+	{ return reinterpret_cast<void*>( mArr->data() ); }
 	virtual SizeT datasize() const override final { return size() * sizeof(T); }
     };
 	
@@ -108,6 +108,9 @@ struct PyCxArrayB
 int PyCxArrayB_init(PyCxArrayB* self, PyObject* args, PyObject* kwds);
 void PyCxArrayB_dealloc(PyCxArrayB* self);
 PyObject* PyCxArrayB_size(PyCxArrayB* self);
+PyObject* PyCxArrayB_range(PyCxArrayB* self);
+PyObject* PyCxArrayB_writeFile(PyCxArrayB* self, PyObject* args, PyObject* kwds);
+PyObject* PyCxArrayB_readFile(PyCxArrayB* self, PyObject* args, PyObject* kwds);
 PyTypeObject* PyCxArrayBType_init();
 
 extern PyMethodDef PyCxArrayB_methods[];
diff --git a/cnorxz/core/lib/array_wrapper.cpp b/cnorxz/core/lib/array_wrapper.cpp
index 6194e68..81b71a9 100644
--- a/cnorxz/core/lib/array_wrapper.cpp
+++ b/cnorxz/core/lib/array_wrapper.cpp
@@ -77,7 +77,9 @@ Format formatFromString(const char* fstr)
     return f;
 }
 
-void PyCxArrayB_writeFile(PyCxArrayB* self, PyObject* args, PyObject* kwds)
+#ifdef HAVE_CEREAL
+
+PyObject* PyCxArrayB_writeFile(PyCxArrayB* self, PyObject* args, PyObject* kwds)
 {
     if(not self->ptrObj->range()){
 	PyErr_SetString(PyExc_RuntimeError, "array not initialized");
@@ -87,26 +89,29 @@ void PyCxArrayB_writeFile(PyCxArrayB* self, PyObject* args, PyObject* kwds)
     char* format = NULL;
 
     if(not PyArg_ParseTupleAndKeywords(args, kwds, "s|s", kwlist, &fname, &format)){
-	return;
+	return NULL;
     }
     const String fn(fname);
     const Format f = formatFromString(format);
     self->ptrObj->writeFile(f, fn);
+    Py_RETURN_NONE;
 }
 
-void PyCxArrayB_readFile(PyCxArrayB* self, PyObject* args, PyObject* kwds)
+PyObject* PyCxArrayB_readFile(PyCxArrayB* self, PyObject* args, PyObject* kwds)
 {
     static char* kwlist[] = { "format", "filename" , NULL };
     char* fname = NULL;
     char* format = NULL;
 
     if(not PyArg_ParseTupleAndKeywords(args, kwds, "s|s", kwlist, &fname, &format)){
-	return;
+	return NULL;
     }
     const String fn(fname);
     const Format f = formatFromString(format);
     self->ptrObj->readFile(f, fn);
+    Py_RETURN_NONE;
 }
+#endif
 
 PyObject* PyCxArrayB_npa(PyCxArrayB* self)
 {
@@ -117,6 +122,10 @@ PyObject* PyCxArrayB_npa(PyCxArrayB* self)
     }
     const SizeT d = self->ptrObj->range()->dim();
     std::vector<npy_intp> dims(d);
+    for(SizeT i = 0; i != dims.size(); ++i){
+	dims[i] = self->ptrObj->range()->sub(i)->size();
+    }
+    // TODO: Do the following for mutable arrays!!!
     /*
     Py_INCREF(self); // keep data alive
     PyObject* o = PyArray_SimpleNewFromData
@@ -129,7 +138,9 @@ PyObject* PyCxArrayB_npa(PyCxArrayB* self)
     //const npy_intp s = PyArray_NBYTES(o);
     const SizeT s = static_cast<SizeT>( PyArray_NBYTES(o) );
     if(s != self->ptrObj->datasize()) {
-	PyErr_SetString(PyExc_RuntimeError, "lib error");
+	PyErr_Format(PyExc_RuntimeError, "lib error %d vs %d", s, self->ptrObj->datasize());
+	//PyErr_SetString(PyExc_RuntimeError, "lib error");
+	return NULL;
     }
     memcpy( data, self->ptrObj->data(), self->ptrObj->datasize() );
     return o;
@@ -156,7 +167,7 @@ PyTypeObject* PyCxArrayBType_init()
     PyCxArrayBType.tp_methods = PyCxArrayB_methods;
     PyCxArrayBType.tp_init = (initproc) PyCxArrayB_init;
     
-    //import_array();
+    import_array();
     
     if(PyType_Ready(&PyCxArrayBType) < 0) {
 	return NULL;