diff --git a/flake.nix b/flake.nix
index 401eb72c..d7a6cd9c 100644
--- a/flake.nix
+++ b/flake.nix
@@ -46,11 +46,11 @@
           pname = "typst";
           version = cargoToml.workspace.package.version;
 
-          rust-toolchain = (fenix.packages.${system}.fromManifestFile rust-manifest).defaultToolchain;
+          rust-toolchain = fenix.packages.${system}.fromManifestFile rust-manifest;
 
           # Crane-based Nix flake configuration.
           # Based on https://github.com/ipetkov/crane/blob/master/examples/trunk-workspace/flake.nix
-          craneLib = (crane.mkLib pkgs).overrideToolchain rust-toolchain;
+          craneLib = (crane.mkLib pkgs).overrideToolchain rust-toolchain.defaultToolchain;
 
           # Typst files to include in the derivation.
           # Here we include Rust files, docs and tests.
@@ -150,10 +150,13 @@
             checks = self'.checks;
             inputsFrom = [ typst ];
 
-            buildInputs = with pkgs; [
-              rust-analyzer
+            buildInputs = [
+              rust-toolchain.rust-analyzer
+              rust-toolchain.rust-src
             ];
 
+            RUST_SRC_PATH = "${rust-toolchain.rust-src}/lib/rustlib/src/rust/library";
+
             packages = [
               # A script for quickly running tests.
               # See https://github.com/typst/typst/blob/main/tests/README.md#making-an-alias