diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 6055ccd..88db05c 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -10,13 +10,23 @@ on:
   #   - cron: '0 0 * * 0'
 
 jobs:
+  nix-build:
+    name: Nix build
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v5
+    - uses: DeterminateSystems/determinate-nix-action@v3
+    - name: build flake
+      run: |
+        nix build .#
+
   build:
     name: GHC ${{ matrix.ghc-version }} on ${{ matrix.os }} / build
     runs-on: ubuntu-latest
     strategy:
       matrix:
         os: [ubuntu-latest]
-        ghc-version: ['9.10', '9.8', '9.4']
+        ghc-version: ['9.10', '9.8', '9.6']
 
         include:
           - os: windows-latest
@@ -25,7 +35,7 @@ jobs:
             ghc-version: '9.8'
 
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v5
 
     - name: Set up GHC ${{ matrix.ghc-version }}
       id: setup
diff --git a/fints2ledger.cabal b/fints2ledger.cabal
index 138cc76..98c325e 100644
--- a/fints2ledger.cabal
+++ b/fints2ledger.cabal
@@ -82,7 +82,7 @@ library fints2ledger-lib
     , filepath >=1.4.2 && <1.6
     , generic-lens >=2.2.2 && <2.3
     , haskeline >=0.8.2 && <0.9
-    , hledger-lib >=1.27.1 && <1.43
+    , hledger-lib >=1.27.1 && <1.51
     , lens >=5.1.1 && <5.4
     , optparse-applicative >=0.17.1 && <0.19
     , regex-tdfa >=1.3.2 && <1.4
@@ -144,7 +144,7 @@ test-suite fints2ledger-test
     , base
     , containers
     , fints2ledger-lib
-    , sydtest >= 0.15 && <= 0.20
+    , sydtest >= 0.15 && <= 0.23
     , transformers
     , text
     , time
diff --git a/flake.lock b/flake.lock
index e7a566b..5410596 100644
--- a/flake.lock
+++ b/flake.lock
@@ -5,11 +5,11 @@
         "nixpkgs-lib": "nixpkgs-lib"
       },
       "locked": {
-        "lastModified": 1741352980,
-        "narHash": "sha256-+u2UunDA4Cl5Fci3m7S643HzKmIDAe+fiXrLqYsR2fs=",
+        "lastModified": 1763759067,
+        "narHash": "sha256-LlLt2Jo/gMNYAwOgdRQBrsRoOz7BPRkzvNaI/fzXi2Q=",
         "owner": "hercules-ci",
         "repo": "flake-parts",
-        "rev": "f4330d22f1c5d2ba72d3d22df5597d123fdb60a9",
+        "rev": "2cccadc7357c0ba201788ae99c4dfa90728ef5e0",
         "type": "github"
       },
       "original": {
@@ -20,11 +20,11 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1742707865,
-        "narHash": "sha256-RVQQZy38O3Zb8yoRJhuFgWo/iDIDj0hEdRTVfhOtzRk=",
+        "lastModified": 1764322985,
+        "narHash": "sha256-bFUcmIbV5EQL4uKRGirtdN+dvH2d3n7YGzmr6U4vZfU=",
         "owner": "nixos",
         "repo": "nixpkgs",
-        "rev": "dd613136ee91f67e5dba3f3f41ac99ae89c5406b",
+        "rev": "44cb8f9588d9823529a12919a3558c3e15b6bb93",
         "type": "github"
       },
       "original": {
@@ -36,11 +36,11 @@
     },
     "nixpkgs-lib": {
       "locked": {
-        "lastModified": 1740877520,
-        "narHash": "sha256-oiwv/ZK/2FhGxrCkQkB83i7GnWXPPLzoqFHpDD3uYpk=",
+        "lastModified": 1761765539,
+        "narHash": "sha256-b0yj6kfvO8ApcSE+QmA6mUfu8IYG6/uU28OFn4PaC8M=",
         "owner": "nix-community",
         "repo": "nixpkgs.lib",
-        "rev": "147dee35aab2193b174e4c0868bd80ead5ce755c",
+        "rev": "719359f4562934ae99f5443f20aa06c2ffff91fc",
         "type": "github"
       },
       "original": {