Wrong cast

This code:

import sympy as sp
import pystencils as ps


field_type = "float64" # if ctx.double_accuracy else "float32"
# ----- Solving the 2D Poisson equation with rhs --------------------------
dx = sp.Symbol("dx")
dy = sp.Symbol("dy")
src, dst, rhs = ps.fields(f"src, src_tmp, rhs: {field_type}[2D]", layout='fzyx')

up = ps.Assignment(src[0, 0], ((dy**2 * (src[1, 0] + src[-1, 0]))
                  + (dx**2 * (src[0, 1] + src[0, -1]))
                  - (rhs[0, 0] * dx**2 * dy**2)) / (2 * (dx**2 + dy**2)))
    
config = ps.CreateKernelConfig(data_type=field_type,
                               cpu_vectorize_info={'instruction_set': 'avx',
                                                   'assume_inner_stride_one': True,
                                                   'assume_aligned': True})
ast = ps.create_kernel(up, config=config)
ast.compile()

leads to NotImplementedError: Vectorizer cannot cast between different datatypes