Error response from daemon: Unknown instruction: XVFB

I am trying to use xfvb to test my node application using nightmareJS, but I'm getting the error

Error response from daemon: Unknown instruction: XVFB

while using this Dockerfile...

Dockerfile

# Get ubuntu packages
RUN apt-get -qq update && \
    apt-get -yqq install \
        libgtk2.0-0 \
        libgconf-2-4 \
        libasound2 \
        libxtst6 \
        libxss1 \
        libnss3 \
        xvfb

# Start Xvfb
Xvfb -ac -screen scrn 1280x2000x24 :9.0 &
export DISPLAY=:9.0

Also tried to use npm

RUN npm install -g xvfb --silent

via user3142695