diff --git a/.ci/scripts/build-all-dev-envs.sh b/.ci/scripts/build-all-dev-envs.sh
index 67f6258..80aa6c4 100755
--- a/.ci/scripts/build-all-dev-envs.sh
+++ b/.ci/scripts/build-all-dev-envs.sh
@@ -5,7 +5,7 @@ PROJECT_FLAKES_DIR="project-flakes"
 set -ex
 
 # Loop through each sub-directory in 'project-flakes'
-for project in "$PROJECT_FLAKES_DIR"/*/ ; do  
+for project in "$PROJECT_FLAKES_DIR"/*/ ; do
   # Remove the trailing '/'
   project=${project%*/}
   # Extract the project name
@@ -24,7 +24,7 @@ for project in "$PROJECT_FLAKES_DIR"/*/ ; do
   # Enter the project directory.
   cd "$project"
   # Show the generated outputs of the flake.
-  nix flake show ..
+  nix flake show --impure ..
   # Attempt to build and enter the development environment,
   # then run the specified test command.
   nix develop --impure ..#"$project" -c bash -c "$cmd"
@@ -32,4 +32,4 @@ for project in "$PROJECT_FLAKES_DIR"/*/ ; do
   cd ..
   # Delete the project directory.
   rm -rf "$project"
-done
\ No newline at end of file
+done
diff --git a/README.md b/README.md
index db8fb90..a890053 100644
--- a/README.md
+++ b/README.md
@@ -40,7 +40,7 @@ installer](https://github.com/DeterminateSystems/nix-installer?tab=readme-ov-fil
 Then at the root of your local Synapse checkout, run the following command:
 
 ```shell
-nix develop impure github:element-hq/nix-flakes#synapse
+nix develop --impure github:element-hq/nix-flakes#synapse
 ```
 
 Dependencies will be downloaded and installed for you, and you'll be dropped
@@ -59,7 +59,7 @@ If typing `nix develop --impure ...` gets tiring, you can automatically enter
 the desired project development environment by installing `direnv` and creating
 a `.envrc` file with the following contents:
 
-```
+```shell
 use flake --impure github:element-hq/nix-flakes#synapse
 ```
 
@@ -145,15 +145,15 @@ language that returns a devenv module. A basic example of a `module.nix`:
 To test a development environment locally without pushing it to git, you can
 use the following to reference a development environment in a local directory:
 
-```
+```shell
 nix develop path:///home/work/code/nix-flakes#synapse --impure
 ```
 
-...which would drop you into a new `synapse` development environment shell.
+... which would drop you into a new `synapse` development environment shell.
 
 The same can be done when using `direnv`. Just set your `.envrc` file to:
 
-```
+```shell
 use flake path:///home/work/code/nix-flakes#synapse --impure
 ```
 
@@ -168,4 +168,4 @@ is where all that happens.
 available options you can specify.
 
 The [Nix Language basics](https://zero-to-nix.com/concepts/nix-language) is a
-recommended read.
\ No newline at end of file
+recommended read.
diff --git a/flake.lock b/flake.lock
index dc07ec6..5c0744a 100644
--- a/flake.lock
+++ b/flake.lock
@@ -333,14 +333,18 @@
     },
     "nixpkgs_3": {
       "locked": {
-        "lastModified": 0,
-        "narHash": "sha256-CyyxvOwFf12I91PBWz43iGT1kjsf5oi6ax7CrvaMyAo=",
-        "path": "/nix/store/yqy82fn77fy3rv7lpwa9m11w3a2nnqg5-source",
-        "type": "path"
+        "lastModified": 1729265718,
+        "narHash": "sha256-4HQI+6LsO3kpWTYuVGIzhJs1cetFcwT7quWCk/6rqeo=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "ccc0c2126893dd20963580b6478d1a10a4512185",
+        "type": "github"
       },
       "original": {
-        "id": "nixpkgs",
-        "type": "indirect"
+        "owner": "NixOS",
+        "ref": "nixpkgs-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
       }
     },
     "nixpkgs_4": {
diff --git a/flake.nix b/flake.nix
index 434bb21..3c61b45 100644
--- a/flake.nix
+++ b/flake.nix
@@ -1,5 +1,7 @@
 {
   inputs = {
+    # Aim for the latest versions of packages by default.
+    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
     # A development environment manager built on Nix. See https://devenv.sh.
     devenv.url = "github:cachix/devenv/v1.0.7";
     # Output a development shell for x86_64/aarch64 Linux/Darwin (MacOS).
@@ -111,4 +113,4 @@
         }
       );
     };
-}
\ No newline at end of file
+}
diff --git a/project-flakes/matrix-hyper-federation-client/module.nix b/project-flakes/matrix-hyper-federation-client/module.nix
index a1d2318..422d835 100644
--- a/project-flakes/matrix-hyper-federation-client/module.nix
+++ b/project-flakes/matrix-hyper-federation-client/module.nix
@@ -7,10 +7,10 @@
   # Search for package names at https://search.nixos.org/packages?channel=unstable
   packages = with pkgs; [
     # The rust toolchain and related tools.
-    (rust-bin.stable."1.66.0".default.override {
+    (rust-bin.stable."1.70.0".default.override {
       extensions = [ "rust-src" ];
     })
-    
+
     # For enabling faster Rust compile times. See the `env` option below.
     clang
     mold
@@ -27,4 +27,4 @@
     # TODO: The lld flags may be Linux-only?
     "RUSTFLAGS" = "-Clinker=clang -Clink-arg=-fuse-ld=${pkgs.mold}/bin/mold";
   };
-}
\ No newline at end of file
+}
diff --git a/project-flakes/synapse/module.nix b/project-flakes/synapse/module.nix
index 651425c..cb3d755 100644
--- a/project-flakes/synapse/module.nix
+++ b/project-flakes/synapse/module.nix
@@ -54,7 +54,7 @@
   # Automatically activate the poetry virtualenv upon entering the shell.
   languages.python.poetry.activate.enable = true;
   # Install all extra Python dependencies; this is needed to run the unit
-  # tests and utilitise all Synapse features.
+  # tests and utilise all Synapse features.
   languages.python.poetry.install.arguments = ["--extras all"];
   # Install the 'matrix-synapse' package from the local checkout.
   languages.python.poetry.install.installRootPackage = true;
@@ -81,8 +81,8 @@
   # Create a postgres user called 'synapse_user' which has ownership
   # over the 'synapse' database.
   services.postgres.initialScript = ''
-  CREATE USER synapse_user;
-  ALTER DATABASE synapse OWNER TO synapse_user;
+    CREATE USER synapse_user;
+    ALTER DATABASE synapse OWNER TO synapse_user;
   '';
 
   # Redis is needed in order to run Synapse in worker mode.
@@ -130,4 +130,4 @@
   enterShell = ''
     unset LD_LIBRARY_PATH
   '';
-}
\ No newline at end of file
+}
diff --git a/project-flakes/sytest/module.nix b/project-flakes/sytest/module.nix
index 42585e3..8984139 100644
--- a/project-flakes/sytest/module.nix
+++ b/project-flakes/sytest/module.nix
@@ -43,7 +43,7 @@
   # corresponding Nix packages on https://search.nixos.org/packages.
   #
   # This was done until `./install-deps.pl --dryrun` produced no output.
-  env.PERL5LIB = "${with pkgs.perl536Packages; makePerlPath [
+  env.PERL5LIB = "${with pkgs.perl538Packages; makePerlPath [
     DBI
     ClassMethodModifiers
     CryptEd25519
@@ -79,4 +79,4 @@
     URI
     YAMLLibYAML
   ]}";
-}
\ No newline at end of file
+}