Can't build from source

[FTDSB]

I tried building the 1.4.0 distribution from source tonight on a Centos 
7.4 machine and I got the following error:

[root@localhost apache-mynewt-newt-1.4.0]# make
./build.sh
Building newt.  This may take a minute...
# mynewt.apache.org/newt/newt/builder
builder/targetbuild.go:380:15: undefined: x509.MarshalPKCS1PublicKey
make: *** [build] Error 1
Thoughts?

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Mike Adams
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