diff --git a/.travis.yml b/.travis.yml
index 54116a76..5c9e45d1 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -35,12 +35,6 @@ matrix:
   include:
   # We grab the appropriate GHC and cabal-install versions from hvr's PPA. See:
   # https://github.com/hvr/multi-ghc-travis
-  - env: BUILD=cabal GHCVER=8.0.2 CABALVER=1.24 HAPPYVER=1.19.5 ALEXVER=3.1.7
-    compiler: ": #GHC 8.0.2"
-    addons: {apt: {packages: [cabal-install-1.24,ghc-8.0.2,happy-1.19.5,alex-3.1.7], sources: [hvr-ghc]}}
-  - env: BUILD=cabal GHCVER=8.2.2 CABALVER=2.0 HAPPYVER=1.19.5 ALEXVER=3.1.7
-    compiler: ": #GHC 8.2.2"
-    addons: {apt: {packages: [cabal-install-2.0,ghc-8.2.2,happy-1.19.5,alex-3.1.7], sources: [hvr-ghc]}}
   - env: BUILD=cabal GHCVER=8.4.4 CABALVER=2.2 HAPPYVER=1.19.5 ALEXVER=3.1.7
     compiler: ": #GHC 8.4.4"
     addons: {apt: {packages: [cabal-install-2.2,ghc-8.4.4,happy-1.19.5,alex-3.1.7], sources: [hvr-ghc]}}
@@ -60,14 +54,6 @@ matrix:
     compiler: ": #stack default"
     addons: {apt: {packages: [libgmp-dev]}}
 
-  - env: BUILD=stack ARGS="--stack-yaml stack-lts-9.yaml --resolver lts-9"
-    compiler: ": #stack 8.0.2"
-    addons: {apt: {packages: [libgmp-dev]}}
-
-  - env: BUILD=stack ARGS="--resolver lts-11"
-    compiler: ": #stack 8.2.2"
-    addons: {apt: {packages: [libgmp-dev]}}
-
   - env: BUILD=stack ARGS="--resolver lts-12"
     compiler: ": #stack 8.4.4"
     addons: {apt: {packages: [libgmp-dev]}}
@@ -76,10 +62,6 @@ matrix:
     compiler: ": #stack 8.6.3"
     addons: {apt: {packages: [libgmp-dev]}}
 
-  - env: BUILD=stack ARGS="--stack-yaml stack-persistent-2-9.yaml"
-    compiler: ": #stack/persistent 2.9"
-    addons: {apt: {packages: [libgmp-dev]}}
-
   # Nightly builds are allowed to fail
   - env: BUILD=stack ARGS="--resolver nightly"
     compiler: ": #stack nightly"
@@ -90,14 +72,6 @@ matrix:
     compiler: ": #stack default osx"
     os: osx
 
-  - env: BUILD=stack ARGS="--stack-yaml stack-lts-9.yaml --resolver lts-9"
-    compiler: ": #stack 8.0.2 osx"
-    os: osx
-
-  - env: BUILD=stack ARGS="--resolver lts-11"
-    compiler: ": #stack 8.2.2 osx"
-    os: osx
-
   - env: BUILD=stack ARGS="--resolver lts-12"
     compiler: ": #stack 8.4.4 osx"
     os: osx
@@ -106,10 +80,6 @@ matrix:
     compiler: ": #stack 8.6.3 osx"
     os: osx
 
-  - env: BUILD=stack ARGS="--stack-yaml stack-persistent-2-9.yaml"
-    compiler: ": #stack/persistent 2.9"
-    os: osx
-
   - env: BUILD=stack ARGS="--resolver nightly"
     compiler: ": #stack nightly osx"
     os: osx
diff --git a/appveyor.yml b/appveyor.yml
index a97d407b..a1ef35d1 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -9,7 +9,7 @@ install:
 build: off
 
 build_script:
-  - stack --no-terminal test --no-run-tests --resolver lts-11
+  - stack --no-terminal test --no-run-tests
 
 test_script:
-  - stack --jobs 1 --no-terminal test --resolver lts-11
+  - stack --jobs 1 --no-terminal test
diff --git a/sources.txt b/sources.txt
deleted file mode 100644
index 1452bfc6..00000000
--- a/sources.txt
+++ /dev/null
@@ -1,13 +0,0 @@
-./yesod-core
-./yesod-static
-./yesod-persistent
-./yesod-newsfeed
-./yesod-form
-./yesod-auth
-./yesod-auth-oauth
-./yesod-sitemap
-./yesod-test
-./yesod-bin
-./yesod
-./yesod-eventsource
-./yesod-websockets
diff --git a/stack-lts-9.yaml b/stack-lts-9.yaml
deleted file mode 100644
index ad311b2e..00000000
--- a/stack-lts-9.yaml
+++ /dev/null
@@ -1,37 +0,0 @@
-resolver: lts-9.21
-packages:
-- ./yesod-core
-- ./yesod-static
-- ./yesod-persistent
-- ./yesod-newsfeed
-- ./yesod-form
-- ./yesod-auth
-- ./yesod-auth-oauth
-- ./yesod-sitemap
-- ./yesod-test
-- ./yesod-bin
-- ./yesod
-- ./yesod-eventsource
-- ./yesod-websockets
-extra-deps:
-- bsb-http-chunked-0.0.0.2@rev:0
-- conduit-1.3.0.2@rev:0
-- conduit-extra-1.3.0@rev:0
-- html-conduit-1.3.0@rev:0
-- http-client-0.5.12.1@rev:0
-- http-conduit-2.3.1@rev:0
-- monad-logger-0.3.28.5@rev:0
-- mono-traversable-1.0.8.1@rev:0
-- persistent-2.8.2@rev:0
-- persistent-sqlite-2.8.1.2@rev:0
-- project-template-0.2.0.1@rev:0
-- resourcet-1.2.1@rev:0
-- streaming-commons-0.2.0.0@rev:0
-- typed-process-0.2.2.0@rev:0
-- unliftio-0.2.7.0@rev:0
-- unliftio-core-0.1.1.0@rev:0
-- wai-extra-3.0.22.1@rev:0
-- wai-logger-2.3.2@rev:0
-- warp-3.2.22@rev:0
-- xml-conduit-1.8.0@rev:0
-- yaml-0.8.30@rev:0
diff --git a/stack-persistent-2-9.yaml b/stack-persistent-2-9.yaml
deleted file mode 100644
index c043213f..00000000
--- a/stack-persistent-2-9.yaml
+++ /dev/null
@@ -1,18 +0,0 @@
-resolver: lts-11.10
-packages:
-- ./yesod-core
-- ./yesod-static
-- ./yesod-persistent
-- ./yesod-newsfeed
-- ./yesod-form
-- ./yesod-auth
-- ./yesod-auth-oauth
-- ./yesod-sitemap
-- ./yesod-test
-- ./yesod-bin
-- ./yesod
-- ./yesod-eventsource
-- ./yesod-websockets
-extra-deps:
-- persistent-2.9.0@rev:0
-- persistent-sqlite-2.9.0@rev:0
diff --git a/yesod-core/yesod-core.cabal b/yesod-core/yesod-core.cabal
index 8c7ff35d..2561c5b9 100644
--- a/yesod-core/yesod-core.cabal
+++ b/yesod-core/yesod-core.cabal
@@ -24,7 +24,7 @@ extra-source-files:
 library
     hs-source-dirs: src
 
-    build-depends:   base                  >= 4.9      && < 5
+    build-depends:   base                  >= 4.11     && < 5
                    , aeson                 >= 1.0
                    , auto-update
                    , blaze-html            >= 0.5