diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 07fb36b9..b7c2ace4 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -9,26 +9,17 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
 
-      - uses: purescript-contrib/setup-purescript@main
+      - uses: cachix/install-nix-action@v27
         with:
-          purescript: "unstable"
+          extra_nix_config: |
+            accept-flake-config = true
+            extra-substituters = https://cache.iog.io https://purescript-lua.cachix.org
+            extra-trusted-public-keys = hydra.iohk.io:f/Ea+s+dFdN+3Y/G+FDgSq+a5NEWhJGzdjvKNGv0/EQ= purescript-lua.cachix.org-1:yLs4ei2HtnuPtzLekOrW3xdfm95+Etw15gwgyIGTayA=
 
-      - uses: actions/setup-node@v2
-        with:
-          node-version: "14.x"
-
-      - name: Install dependencies
-        run: |
-          npm install -g bower
-          npm install
-          bower install --production
-
-      - name: Build source
-        run: npm run-script build
+      - name: Build
+        run: nix develop -c ./scripts/build
 
-      - name: Run tests
-        run: |
-          bower install
-          npm run-script test --if-present
+      - name: Luacheck
+        run: nix develop -c luacheck --quiet --std min src/
diff --git a/src/Data/Bounded.lua b/src/Data/Bounded.lua
index 296d6fc8..e723c5a2 100644
--- a/src/Data/Bounded.lua
+++ b/src/Data/Bounded.lua
@@ -1,8 +1,14 @@
+-- Lua 5.1 compatibility:
+-- * math.maxinteger/math.mininteger appeared in Lua 5.3; PureScript Int
+--   is a 32-bit integer, so its bounds are spelled out literally.
+-- * "\u{...}" escapes appeared in Lua 5.3 (PUC Lua 5.1 silently reads
+--   "\u" as "u"). A Char is a single byte in pslua, so its bounds are
+--   the byte bounds.
 return {
-  topInt = (math.maxinteger),
-  bottomInt = (math.mininteger),
-  topChar = ("\u{FFFF}"),
-  bottomChar = ("\u{0000}"),
+  topInt = (2147483647),
+  bottomInt = (-2147483648),
+  topChar = ("\255"),
+  bottomChar = ("\0"),
   topNumber = (1 / 0),
   bottomNumber = (-1 / 0)
 }
diff --git a/src/Data/EuclideanRing.lua b/src/Data/EuclideanRing.lua
index a600582c..e419766f 100644
--- a/src/Data/EuclideanRing.lua
+++ b/src/Data/EuclideanRing.lua
@@ -1,5 +1,6 @@
 return {
-  intDegree = (function(x) return math.min(math.abs(x), math.maxinteger) end),
+  -- math.maxinteger is Lua 5.3+; PureScript Int is 32-bit
+  intDegree = (function(x) return math.min(math.abs(x), 2147483647) end),
   intDiv = (function(x)
     return function(y)
       if y == 0 then return 0 end
diff --git a/src/Data/Show.lua b/src/Data/Show.lua
index 33112071..bf3446ec 100644
--- a/src/Data/Show.lua
+++ b/src/Data/Show.lua
@@ -4,14 +4,14 @@ return {
   showCharImpl = (function(n)
     local code = n:byte()
     if code < 0x20 or code == 0x7F then
-      if n == "\x07" then return "'\\a'" end
+      if n == "\a" then return "'\\a'" end
       if n == "\b" then return "'\\b'" end
       if n == "\f" then return "'\\f'" end
       if n == "\n" then return "'\\n'" end
       if n == "\r" then return "'\\r'" end
       if n == "\t" then return "'\\t'" end
       if n == "\v" then return "'\\v'" end
-      return "'\\" .. code:toString(10) .. "'"
+      return "'\\" .. tostring(code) .. "'"
     end
     if n == "'" or n == "\\" then return "'\\" .. n .. "'" end
     return "'" .. n .. "'"
@@ -21,7 +21,7 @@ return {
     return function(xs)
       local l = #xs
       local ss = {}
-      for i = 1, l do ss[i] = f(xs[i - 1]) end
+      for i = 1, l do ss[i] = f(xs[i]) end
       return "[" .. table.concat(ss, ",") .. "]"
     end
   end)