diff --git a/Dockerfile b/Dockerfile
index 5eb997d..30fc0d5 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -3,7 +3,9 @@ MAINTAINER github@erebe.eu
 
 RUN apk --no-cache add --repository http://dl-cdn.alpinelinux.org/alpine/edge/community \
         ca-certificates git ghc upx curl musl-dev gmp-dev zlib-dev pcre-dev
-RUN curl -sSL https://get.haskellstack.org/ | sh
+RUN curl -sSL https://github.com/commercialhaskell/stack/releases/download/v1.6.5/stack-1.6.5-linux-x86_64-static.tar.gz | tar xvz && \
+    mv stack*/stack /usr/bin
+
 
 COPY stack.yaml /mnt
 COPY *.cabal /mnt
diff --git a/stack.yaml b/stack.yaml
index ca707c7..bcb2b35 100644
--- a/stack.yaml
+++ b/stack.yaml
@@ -2,7 +2,7 @@
 #
 # Some commonly used options have been documented as comments in this file.
 # For advanced use and comprehensive documentation of the format, please see:
-# http://docs.haskellstack.org/en/stable/yaml_configuration/
+# https://docs.haskellstack.org/en/stable/yaml_configuration/
 
 # Resolver to choose a 'specific' stackage snapshot or a compiler version.
 # A snapshot resolver dictates the compiler version and the set of packages
@@ -27,32 +27,28 @@ resolver: lts-9.9
 #    git: https://github.com/commercialhaskell/stack.git
 #    commit: e7b331f14bcffb8367cd58fbfc8b40ec7642100a
 # - location: https://github.com/commercialhaskell/stack/commit/e7b331f14bcffb8367cd58fbfc8b40ec7642100a
-#   extra-dep: true
 #  subdirs:
 #  - auto-update
 #  - wai
-#
-# A package marked 'extra-dep: true' will only be built if demanded by a
-# non-dependency (i.e. a user package), and its test suites and benchmarks
-# will not be run. This is useful for tweaking upstream packages.
 packages:
-- '.'
+- .
 # Dependency packages to be pulled from upstream that are not in the resolver
+# using the same syntax as the packages field.
 # (e.g., acme-missiles-0.3)
-extra-deps: []
+extra-deps: [ websockets-0.12.4.1 ]
 
 # Override default flag values for local packages and extra-deps
-flags: {}
+# flags: {}
 
 # Extra package databases containing global packages
-extra-package-dbs: []
+# extra-package-dbs: []
 
 # Control whether we use the GHC we find on the path
 # system-ghc: true
 #
 # Require a specific version of stack, using version ranges
 # require-stack-version: -any # Default
-# require-stack-version: ">=1.1"
+# require-stack-version: ">=1.7"
 #
 # Override the architecture used by stack, especially useful on Windows
 # arch: i386
diff --git a/wstunnel.cabal b/wstunnel.cabal
index b101eb5..6a10251 100644
--- a/wstunnel.cabal
+++ b/wstunnel.cabal
@@ -31,7 +31,7 @@ library
                      , streaming-commons
                      , text >= 1.2.2.1
                      , unordered-containers
-                     , websockets
+                     , websockets >= 0.12.4.0
 
   default-language:    Haskell2010