diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 5661983..d5b65f9 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -6,6 +6,10 @@ on:
   pull_request:
   workflow_dispatch:
 
+concurrency: # Cancel stale PR builds (but not push builds)
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.sha }}
+  cancel-in-progress: true
+
 jobs:
   build:
     strategy:
@@ -43,10 +47,10 @@ jobs:
 
     name: '${{ matrix.target.os }}-${{ matrix.target.cpu }} (Nim ${{ matrix.branch }})'
     runs-on: ${{ matrix.builder }}
-    continue-on-error: ${{ matrix.branch == 'version-1-6' || matrix.branch == 'devel' }}
+    continue-on-error: ${{ matrix.branch == 'devel' }}
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
 
       - name: Install build dependencies (Linux i386)
         if: runner.os == 'Linux' && matrix.target.cpu == 'i386'
@@ -94,23 +98,23 @@ jobs:
         id: windows-dlls-cache
         uses: actions/cache@v2
         with:
-          path: external/dlls
-          key: 'dlls'
+          path: external/dlls-${{ matrix.target.cpu }}
+          key: 'dlls-${{ matrix.target.cpu }}'
 
-      - name: Install DLL dependencies (Windows)
+      - name: Install DLLs dependencies (Windows)
         if: >
           steps.windows-dlls-cache.outputs.cache-hit != 'true' &&
           runner.os == 'Windows'
         run: |
-          mkdir external
+          mkdir -p external
           curl -L "https://nim-lang.org/download/windeps.zip" -o external/windeps.zip
-          7z x external/windeps.zip -oexternal/dlls
+          7z x -y external/windeps.zip -oexternal/dlls-${{ matrix.target.cpu }}
 
       - name: Path to cached dependencies (Windows)
         if: >
           runner.os == 'Windows'
         run: |
-          echo '${{ github.workspace }}'"/external/dlls" >> $GITHUB_PATH
+          echo "${{ github.workspace }}/external/dlls-${{ matrix.target.cpu }}" >> $GITHUB_PATH
 
       - name: Derive environment variables
         run: |
@@ -152,5 +156,5 @@ jobs:
           nim --version
           nimble --version
           nimble install -y --depsOnly
-          env TEST_LANG="c" nimble test
-          env TEST_LANG="cpp" nimble test
+          env NIMLANG=c nimble test
+          env NIMLANG=cpp nimble test
diff --git a/faststreams.nimble b/faststreams.nimble
index 48a3657..7dfaa0a 100644
--- a/faststreams.nimble
+++ b/faststreams.nimble
@@ -12,37 +12,27 @@ requires "nim >= 1.2.0",
          "chronos",
          "unittest2"
 
-### Helper functions
-proc test(args, path: string) =
-  # Compilation language is controlled by TEST_LANG
-  let lang = getEnv("TEST_LANG", "c")
+let nimc = getEnv("NIMC", "nim") # Which nim compiler to use
+let lang = getEnv("NIMLANG", "c") # Which backend (c/cpp/js)
+let flags = getEnv("NIMFLAGS", "") # Extra flags for the compiler
+let verbose = getEnv("V", "") notin ["", "0"]
 
-  # nnkArglist was changed to nnkArgList, so can't always use --styleCheck:error
-  # https://github.com/nim-lang/Nim/pull/17529
-  # https://github.com/nim-lang/Nim/pull/19822
-  let styleCheckStyle =
-    if (NimMajor, NimMinor) < (1, 6):
-      "hint"
-    else:
-      "error"
+let styleCheckStyle = if (NimMajor, NimMinor) < (1, 6): "hint" else: "error"
+let cfg =
+  " --styleCheck:usages --styleCheck:" & styleCheckStyle &
+  (if verbose: "" else: " --verbosity:0 --hints:off") &
+  " --skipParentCfg --skipUserCfg --outdir:build --nimcache:build/nimcache -f"
 
-  var common_args = "-r -f " & getEnv("NIMFLAGS") &  " --hints:off --styleCheck:usages --styleCheck:" & styleCheckStyle
+proc build(args, path: string) =
+  exec nimc & " " & lang & " " & cfg & " " & flags & " " & args & " " & path
 
-  if getEnv("NIMBUS_ENV_DIR") != "":
-    common_args &= " --skipParentCfg"
-
-  exec "nim " & lang & " " & args &
-    " -d:asyncBackend=none " & common_args & " " & path
-  exec "nim " & lang & " " & args &
-    " -d:asyncBackend=chronos " & common_args & " " & path
-  # TODO std backend is broken / untested
-  # exec "nim " & lang & " " & args &
-  #  " -d:asyncBackend=asyncdispatch " & common_args & " " & path
+proc run(args, path: string) =
+  build args & " -r", path
 
 task test, "Run all tests":
-  test "-d:debug   --threads:off", "tests/all_tests"
-  test "-d:release --threads:off", "tests/all_tests"
-  test "-d:danger  --threads:off", "tests/all_tests"
-  test "-d:debug   --threads:on", "tests/all_tests"
-  test "-d:release --threads:on", "tests/all_tests"
-  test "-d:danger  --threads:on", "tests/all_tests"
+  # TODO asyncdispatch backend is broken / untested
+  for backend in ["-d:asyncBackend=none", "-d:asyncBackend=chronos"]:
+    for threads in ["--threads:off", "--threads:on"]:
+      for mode in ["-d:debug", "-d:release", "-d:danger"]:
+        run backend & " " & threads & " " & mode, "tests/all_tests"
+
diff --git a/faststreams/buffers.nim b/faststreams/buffers.nim
index d7747b7..a86a880 100644
--- a/faststreams/buffers.nim
+++ b/faststreams/buffers.nim
@@ -1,6 +1,6 @@
 import
   deques,
-  stew/[ptrops, ranges/ptr_arith],
+  stew/ptrops,
   async_backend
 
 export
diff --git a/faststreams/inputs.nim b/faststreams/inputs.nim
index e646338..f1f0b5d 100644
--- a/faststreams/inputs.nim
+++ b/faststreams/inputs.nim
@@ -1,6 +1,6 @@
 import
   os, memfiles, options,
-  stew/[ptrops, ranges/ptr_arith],
+  stew/[ptrops],
   async_backend, buffers
 
 export
diff --git a/faststreams/outputs.nim b/faststreams/outputs.nim
index f24d297..0903aed 100644
--- a/faststreams/outputs.nim
+++ b/faststreams/outputs.nim
@@ -8,7 +8,7 @@
 
 import
   deques, typetraits,
-  stew/[ptrops, strings, ranges/ptr_arith],
+  stew/[ptrops, strings],
   buffers, async_backend
 
 export
diff --git a/faststreams/textio.nim b/faststreams/textio.nim
index 9bdd449..7360ff4 100644
--- a/faststreams/textio.nim
+++ b/faststreams/textio.nim
@@ -126,7 +126,7 @@ const
   NewLines* = {'\r', '\n'}
   Digits* = {'0'..'9'}
 
-proc readLine*(s: InputStream, keepEol = false): TaintedString {.fsMultiSync.} =
+proc readLine*(s: InputStream, keepEol = false): string {.fsMultiSync.} =
   fsAssert readableNow(s)
 
   while s.readable:
@@ -145,7 +145,7 @@ proc readLine*(s: InputStream, keepEol = false): TaintedString {.fsMultiSync.} =
     result.add s.read.char
 
 proc readUntil*(s: InputStream,
-                sep: openArray[char]): Option[TaintedString] =
+                sep: openArray[char]): Option[string] =
   fsAssert readableNow(s)
   var res = ""
   while s.readable(sep.len):
@@ -153,14 +153,14 @@ proc readUntil*(s: InputStream,
       return some(res)
     res.add s.read.char
 
-template nextLine*(sp: InputStream, keepEol = false): Option[TaintedString] =
+template nextLine*(sp: InputStream, keepEol = false): Option[string] =
   let s = sp
   if s.readable:
     some readLine(s, keepEol)
   else:
     none string
 
-iterator lines*(s: InputStream, keepEol = false): TaintedString =
+iterator lines*(s: InputStream, keepEol = false): string =
   while s.readable:
     yield readLine(s, keepEol)
 
diff --git a/tests/test_inputs.nim b/tests/test_inputs.nim
index da9dbaa..4e69058 100644
--- a/tests/test_inputs.nim
+++ b/tests/test_inputs.nim
@@ -4,7 +4,7 @@ import
   os, unittest2, strutils, random,
   ../faststreams, ../faststreams/textio
 
-setCurrentDir getAppDir()
+setCurrentDir currentSourcePath.parentDir
 
 proc str(bytes: openArray[byte]): string =
   result = newStringOfCap(bytes.len)
diff --git a/tests/test_outputs.nim b/tests/test_outputs.nim
index 7c1003b..e438099 100644
--- a/tests/test_outputs.nim
+++ b/tests/test_outputs.nim
@@ -2,7 +2,7 @@
 
 import
   os, unittest2, random, strformat,
-  stew/ranges/ptr_arith,
+  stew/ptrops,
   ../faststreams, ../faststreams/textio
 
 proc bytes(s: string): seq[byte] =