People seem to overestimate the security of SHA256 as compared to SHA1.
Although it is definitely better than SHA1, the improvement is ever so slightly:
SHA1 : ec1623b7a94ed3d8feaffaf7580df3eca4f5f5ca
SHA256 : e2b0c44298fc0c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855