Fails to build on travis-ci environment

[iustin]

I tried installing via a sandboxed env, and as you can see in the build log, it fails to build with:

…
[ 7 of 11] Compiling Trace.Hpc.Coveralls.Curl ( src/Trace/Hpc/Coveralls/Curl.hs, dist/dist-sandbox-ed1f6b59/build/hpc-coveralls/hpc-coveralls-tmp/Trace/Hpc/Coveralls/Curl.o )
src/Trace/Hpc/Coveralls/Curl.hs:36:25:
    Not in scope: `decode'
    Perhaps you meant `encode' (imported from Data.Aeson)
cabal: Leaving directory '/tmp/cabal-tmp-6387/hpc-coveralls-0.9.0'
cabal: Error: some packages failed to install:
hpc-coveralls-0.9.0-Cwr3C23BEBV6lbgspZChJV failed during the building phase.
The exception was:
ExitFailure 1

However, I can't reproduce this locally (on Debian unstable). Have you seen/heard this before?