[CentOS-devel] error: COS74: nss-softokn, ec.c, ECCurve25519 undeclared

I build nss and nss-softokn on a regular basis and follow the updates.
I am seeing this new error with nss-softokn-3.28.3-8.el7_4.src.rpm

ec.c:21:7: error: 'ECCurve25519' undeclared here (not in a function)
     { ECCurve25519,

Does this ring any bells? Or any suggestion appreciated.
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