diff --git a/Makefile b/Makefile
index 201581d1..7f71ab15 100644
--- a/Makefile
+++ b/Makefile
@@ -46,9 +46,8 @@ endif
 .PHONY: setup
 setup: setup-qemu
 	rustup install stable
-	cargo +stable install elf2tab
-	cargo miri setup
-	rustup target add --toolchain stable thumbv7em-none-eabi
+	cargo install elf2tab
+	cargo +nightly miri setup
 
 # Sets up QEMU in the tock/ directory. We use Tock's QEMU which may contain
 # patches to better support boards that Tock supports.
@@ -108,19 +107,8 @@ EXCLUDE_STD := --exclude libtock_unittest --exclude print_sizes \
                --exclude runner --exclude syscalls_tests \
                --exclude libtock_build_scripts
 
-# Currently, all of our crates should build with a stable toolchain. This
-# verifies our crates don't depend on unstable features by using cargo check. We
-# specify a different target directory so this doesn't flush the cargo cache of
-# the primary toolchain.
-.PHONY: test-stable
-test-stable:
-	cargo +stable check --target-dir=target/stable --workspace \
-		$(EXCLUDE_RUNTIME)
-	LIBTOCK_PLATFORM=nrf52 cargo +stable check $(EXCLUDE_STD) \
-		--target=thumbv7em-none-eabi --target-dir=target/stable --workspace
-
 .PHONY: test
-test: examples test-stable
+test: examples
 	cargo test $(EXCLUDE_RUNTIME) --workspace
 	LIBTOCK_PLATFORM=nrf52 cargo fmt --all -- --check
 	cargo clippy --all-targets $(EXCLUDE_RUNTIME) --workspace
@@ -129,7 +117,7 @@ test: examples test-stable
 	LIBTOCK_PLATFORM=hifive1 cargo clippy $(EXCLUDE_STD) \
 		--target=riscv32imac-unknown-none-elf --workspace
 	MIRIFLAGS="-Zmiri-strict-provenance -Zmiri-symbolic-alignment-check" \
-		cargo miri test $(EXCLUDE_MIRI) --workspace
+		cargo +nightly miri test $(EXCLUDE_MIRI) --workspace
 	echo '[ SUCCESS ] libtock-rs tests pass'
 
 # Helper functions to define make targets to build for specific (flash, ram,
diff --git a/platform/src/register.rs b/platform/src/register.rs
index 976653a5..0afde2f1 100644
--- a/platform/src/register.rs
+++ b/platform/src/register.rs
@@ -1,3 +1,5 @@
+use core::mem::transmute;
+
 /// In order to work with Miri's `-Zmiri-track-raw-pointers` flag, we cannot
 /// pass pointers to the kernel through `usize` values (as casting to and from
 /// `usize` drops the pointer`s tag). Instead, `RawSyscalls` uses the `Register`
@@ -16,19 +18,28 @@ pub struct Register(pub *mut ());
 
 impl From<crate::ErrorCode> for Register {
     fn from(value: crate::ErrorCode) -> Register {
-        Register(value as u16 as *mut ())
+        (value as usize).into()
     }
 }
 
 impl From<u32> for Register {
     fn from(value: u32) -> Register {
-        Register(value as *mut ())
+        (value as usize).into()
     }
 }
 
 impl From<usize> for Register {
     fn from(value: usize) -> Register {
-        Register(value as *mut ())
+        // Note: clippy is wrong here; transmute has different semantics than
+        // `as` casts under strict provenance.
+        #[allow(clippy::useless_transmute)]
+        // We want to convert using the same semantics as core::ptr::invalid:
+        // convert the usize into a pointer with that address without attaching
+        // provenance to it. However, core::ptr::invalid is a nightly-only
+        // function. In order to build on stable, we copy its implementation.
+        // Safety: Raw pointers do not have any validity invariants that usize
+        // does not have; a raw pointer can point to any address.
+        Register(unsafe { transmute(value) })
     }
 }
 
diff --git a/rust-toolchain b/rust-toolchain
index 4c36818b..a9b2b057 100644
--- a/rust-toolchain
+++ b/rust-toolchain
@@ -1,8 +1,6 @@
 [toolchain]
-# See https://rust-lang.github.io/rustup-components-history/ for a list of
-# recently nightlies and what components are available for them.
-channel = "nightly-2022-06-10"
-components = ["clippy", "miri", "rustfmt"]
+channel = "stable"
+components = ["clippy", "rustfmt"]
 targets = ["thumbv6m-none-eabi",
            "thumbv7em-none-eabi",
            "riscv32imac-unknown-none-elf",
diff --git a/unittest/Cargo.toml b/unittest/Cargo.toml
index 3a7eb5f0..094f0915 100644
--- a/unittest/Cargo.toml
+++ b/unittest/Cargo.toml
@@ -10,4 +10,4 @@ version = "0.1.0"
 
 [dependencies]
 libtock_platform = { path = "../platform" }
-thiserror = "1.0"
+thiserror = "1.0.44"