diff --git a/.github/workflows/sdk.yaml b/.github/workflows/sdk.yaml
index 53613534e..76b5a31f7 100644
--- a/.github/workflows/sdk.yaml
+++ b/.github/workflows/sdk.yaml
@@ -33,10 +33,6 @@ jobs:
             path: seL4
       - name: Install SDK dependencies
         run: |
-          rustup target add x86_64-unknown-linux-musl
-          rustup component add rust-src --toolchain stable-x86_64-unknown-linux-gnu
-          rustup target add aarch64-unknown-linux-musl
-          rustup component add rust-src --toolchain stable-aarch64-unknown-linux-musl
           sudo apt update
           sudo apt install software-properties-common
           sudo add-apt-repository ppa:deadsnakes/ppa
diff --git a/build_sdk.py b/build_sdk.py
index a6d555d47..5d8ebd7a2 100644
--- a/build_sdk.py
+++ b/build_sdk.py
@@ -760,12 +760,16 @@ def build_initialiser(
     component_build_dir = build_dir / board.name / config.name / component_name
     component_build_dir.mkdir(exist_ok=True, parents=True)
 
+    toolchain_setup = "cd tool/microkit && rustup toolchain install && cd ../../"
+
     if custom_rust_sel4_dir is None:
         capdl_init_elf = component_build_dir / "bin" / "sel4-capdl-initializer.elf"
         cmd = f"""
+            {toolchain_setup} && \
             RUSTC_BOOTSTRAP=1 \
-            RUST_TARGET_PATH={rust_target_path} SEL4_PREFIX={sel4_src_dir.absolute()} \
-            cargo install {cargo_cross_options} \
+            RUST_TARGET_PATH={rust_target_path} \
+            SEL4_PREFIX={sel4_src_dir.absolute()} \
+            cargo +1.90.0 install {cargo_cross_options} \
             --target {cargo_target} \
             --locked \
             --git https://github.com/au-ts/rust-seL4 --branch capdl_dev sel4-capdl-initializer --rev 118c9cd67d3a7c95431a0aeb08d8ce8692ab9d80 \
@@ -775,8 +779,9 @@ def build_initialiser(
     else:
         capdl_init_elf = custom_rust_sel4_dir / "target" / cargo_target / "release" / "sel4-capdl-initializer.elf"
         cmd = f"""
+            {toolchain_setup} && /
             cd {custom_rust_sel4_dir} && SEL4_PREFIX={sel4_src_dir.absolute()} \
-            cargo build {cargo_cross_options} --target {cargo_target} \
+            cargo +1.90.0 build {cargo_cross_options} --target {cargo_target} \
             --release -p sel4-capdl-initializer
         """
 
diff --git a/flake.lock b/flake.lock
index bc19ab9f2..bdd2a8a64 100644
--- a/flake.lock
+++ b/flake.lock
@@ -45,11 +45,11 @@
         "nixpkgs": "nixpkgs_2"
       },
       "locked": {
-        "lastModified": 1753671061,
-        "narHash": "sha256-IU4eBWfe9h2QejJYST+EAlhg8a1H6mh9gbcmWgZ2/mQ=",
+        "lastModified": 1762310305,
+        "narHash": "sha256-EW7xlGJnCW3mKujn/F8me52NXB4nBtabArsRNwehtHM=",
         "owner": "oxalica",
         "repo": "rust-overlay",
-        "rev": "40065d17ee4dbec3ded8ca61236132aede843fab",
+        "rev": "4e8e5dfb8e649d3e05d9a173ce9a9cb0498e89c2",
         "type": "github"
       },
       "original": {
diff --git a/flake.nix b/flake.nix
index 5a3f9268d..0cfae4224 100644
--- a/flake.nix
+++ b/flake.nix
@@ -49,22 +49,7 @@
           ps.setuptools
         ]);
 
-        microkitToolToml = nixpkgs.lib.trivial.importTOML ./tool/microkit/Cargo.toml;
-        microkitToolVersion = microkitToolToml.package.rust-version;
-
-        # Unfortunately Cargo does not support all targets by default so for cross-compiling
-        # we must explicitly add certain targets.
-        rustAdditionalTargets = {
-          aarch64-darwin = [ "x86_64-apple-darwin" ];
-          x86_64-darwin = [ "aarch64-apple-darwin" ];
-          x86_64-linux = [];
-          aarch64-linux = [];
-        }.${system} or (throw "Unsupported system: ${system}");
-
-        rustTool = pkgs.rust-bin.stable.${microkitToolVersion}.default.override {
-          extensions = [ "rust-src" ];
-          targets = [ pkgs.pkgsStatic.hostPlatform.rust.rustcTarget ] ++ rustAdditionalTargets;
-        };
+        rustTool = pkgs.rust-bin.fromRustupToolchainFile ./tool/microkit/rust-toolchain.toml;
       in
       {
         # for `nix fmt`
diff --git a/tool/microkit/rust-toolchain.toml b/tool/microkit/rust-toolchain.toml
new file mode 100644
index 000000000..ff666d14a
--- /dev/null
+++ b/tool/microkit/rust-toolchain.toml
@@ -0,0 +1,10 @@
+#
+# Copyright 2025, UNSW
+#
+# SPDX-License-Identifier: BSD-2-Clause
+#
+
+[toolchain]
+channel = "1.90.0"
+components = [ "rustfmt", "rust-src", "rustc-dev", "llvm-tools-preview", "clippy" ]
+targets = ["x86_64-unknown-linux-gnu", "x86_64-unknown-linux-musl", "aarch64-unknown-linux-musl", "x86_64-apple-darwin", "aarch64-apple-darwin"]