diff --git a/nix/src.json b/nix/src.json
index d3b2c93..2585822 100644
--- a/nix/src.json
+++ b/nix/src.json
@@ -1,6 +1,6 @@
 {
   "owner": "NixOS",
   "repo": "nixpkgs",
-  "rev": "7098bcac278a2d028036bb3a23508fd1c52155ac",
-  "sha256": "04m7z7334mjma0ci3vp4js6rbz4s2jxy864s1v4dkdm7860zjc28"
+  "rev": "dbb9f8818af7cf2ea91b89f7d80a8fb1800cbfb5",
+  "sha256": "1i8lsiscjzq066p02a5c7azjrvqxqkz6dipzkkyhh9rmhgs1aca3"
 }
diff --git a/nix/update b/nix/update
index 734e09c..30ad138 100755
--- a/nix/update
+++ b/nix/update
@@ -7,7 +7,7 @@ set -euo pipefail
 
 cd "$(dirname "$0")" || exit 1
 
-branch=release-17.09
+branch=release-18.04
 
 owner=NixOS
 repo=nixpkgs
diff --git a/shell.nix b/shell.nix
index c411ecf..8a8937c 100644
--- a/shell.nix
+++ b/shell.nix
@@ -11,8 +11,8 @@ let
   pkgs = import nixpkgs {};
 in
   pkgs.haskell.lib.buildStackProject {
-    # Either use specified GHC or use GHC 8.2.2 (which we need for LTS 11.9)
-    ghc = if isNull ghc then pkgs.haskell.compiler.ghc822 else ghc;
+    # Either use specified GHC or use GHC 8.4.4 (which we need for LTS 12.26)
+    ghc = if isNull ghc then pkgs.haskell.compiler.ghc844 else ghc;
     extraArgs = "--system-ghc";
     name = "tf-env";
     buildInputs = with pkgs; [ snappy zlib protobuf libtensorflow ];
diff --git a/stack.yaml b/stack.yaml
index abd130c..c791719 100644
--- a/stack.yaml
+++ b/stack.yaml
@@ -1,4 +1,4 @@
-resolver: lts-11.9
+resolver: lts-12.26
 
 packages:
 - tensorflow
@@ -14,12 +14,7 @@ packages:
 - tensorflow-test
 
 extra-deps:
-- snappy-framing-0.1.1
-- snappy-0.2.0.2
-- proto-lens-protobuf-types-0.3.0.1
-- proto-lens-protoc-0.3.1.0
-- proto-lens-0.3.1.0
-- lens-labels-0.2.0.1
+- snappy-framing-0.1.2
 
 # For Mac OS X, whose linker doesn't use this path by default
 # unless you run `xcode-select --install`.
diff --git a/tensorflow-opgen/src/TensorFlow/OpGen.hs b/tensorflow-opgen/src/TensorFlow/OpGen.hs
index 749b118..26de70a 100644
--- a/tensorflow-opgen/src/TensorFlow/OpGen.hs
+++ b/tensorflow-opgen/src/TensorFlow/OpGen.hs
@@ -71,9 +71,9 @@ import Proto.Tensorflow.Core.Framework.OpDef_Fields
 import Proto.Tensorflow.Core.Framework.Types (DataType(..))
 import System.FilePath (takeBaseName)
 import TensorFlow.OpGen.ParsedOp
+import Data.Semigroup ((<>))
 import Text.PrettyPrint.Mainland
   ( Doc
-  , (<>)
   , (<+>)
   , (</>)
   , (<+/>)