diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 121d0938..b5317560 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -41,9 +41,12 @@ jobs:
     - name: Check that all crates build
       run: RUSTFLAGS='--deny warnings' cargo check --all
       shell: bash
+    - name: Check that crates build with unstable-test feature
+      run: RUSTFLAGS='--deny warnings' cargo check --all --features unstable-test
+      shell: bash
     - name: Run tests on Ubuntu/Windows
       if: matrix.os != 'macOS-latest'
-      run: cargo test --workspace
+      run: cargo test --workspace --features unstable-test
     - name: Run tests on macOS
       # NOTE defmt does not build for macOS because its `cortex-m-rt` dependency doesn't
       # (see https://github.com/rust-embedded/cortex-m-rt/issues/74), so we cannot use
@@ -97,7 +100,7 @@ jobs:
       with:
         mdbook-version: latest
     - name: Build defmt
-      run: cargo build
+      run: cargo build --features unstable-test
       # NOTE order of steps is important
     - name: Run book tests
       working-directory: book
diff --git a/Cargo.toml b/Cargo.toml
index 9055e000..62df82ec 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -14,6 +14,9 @@ version = "0.1.3"
 [features]
 alloc = []
 
+# WARNING: for internal use only, not covered by semver guarantees
+unstable-test = ["defmt-macros/unstable-test"]
+
 [dependencies]
 defmt-macros = { path = "macros", version = "0.1.1" }
 heapless = "0.5.6"
diff --git a/book/src/introduction.md b/book/src/introduction.md
index f2b9a175..71526611 100644
--- a/book/src/introduction.md
+++ b/book/src/introduction.md
@@ -14,8 +14,6 @@
 - Output object format must be ELF
 - Custom linking (linker script) is required
 - Single, global logger instance (but using multiple channels is possible)
-- No x86 support. The x86 architecture is exclusively used for testing at the
-  moment.
 
 ## Intended use
 
diff --git a/macros/Cargo.toml b/macros/Cargo.toml
index 0e5b86d2..9e059ff5 100644
--- a/macros/Cargo.toml
+++ b/macros/Cargo.toml
@@ -12,6 +12,10 @@ version = "0.1.1"
 [lib]
 proc-macro = true
 
+[features]
+# WARNING: for internal use only, not covered by semver guarantees
+unstable-test = []
+
 [dependencies]
 defmt-parser = { path = "../parser", features = ["unstable"], version = "0.1.0" }
 quote = "1.0.7"
diff --git a/macros/src/lib.rs b/macros/src/lib.rs
index be474d98..cd389ca9 100644
--- a/macros/src/lib.rs
+++ b/macros/src/lib.rs
@@ -594,7 +594,10 @@ pub fn assert_(ts: TokenStream) -> TokenStream {
             Level::Error,
             FormatArgs {
                 litstr: LitStr::new(
-                    &format!("panicked at 'assertion failed: {}'", escape_expr(&condition)),
+                    &format!(
+                        "panicked at 'assertion failed: {}'",
+                        escape_expr(&condition)
+                    ),
                     Span2::call_site(),
                 ),
                 rest: None,
@@ -923,19 +926,16 @@ pub fn internp(ts: TokenStream) -> TokenStream {
     let sym = symbol::Symbol::new("prim", &ls).mangle();
     let section = format!(".defmt.prim.{}", sym);
 
-    quote!(match () {
-        #[cfg(target_arch = "x86_64")]
-        () => {
-            defmt::export::fetch_add_string_index() as u8
-        }
-        #[cfg(not(target_arch = "x86_64"))]
-        () => {
+    if cfg!(feature = "unstable-test") {
+        quote!({ defmt::export::fetch_add_string_index() as u8 })
+    } else {
+        quote!({
             #[link_section = #section]
             #[export_name = #sym]
             static S: u8 = 0;
             &S as *const u8 as u8
-        }
-    })
+        })
+    }
     .into()
 }
 
@@ -991,19 +991,16 @@ fn mksym(string: &str, tag: &str, is_log_statement: bool) -> TokenStream2 {
     } else {
         format_ident!("S")
     };
-    quote!(match () {
-        #[cfg(target_arch = "x86_64")]
-        () => {
-            defmt::export::fetch_add_string_index()
-        }
-        #[cfg(not(target_arch = "x86_64"))]
-        () => {
+    if cfg!(feature = "unstable-test") {
+        quote!({ defmt::export::fetch_add_string_index() })
+    } else {
+        quote!({
             #[link_section = #section]
             #[export_name = #sym]
             static #varname: u8 = 0;
             &#varname as *const u8 as usize
-        }
-    })
+        })
+    }
 }
 
 struct Write {
diff --git a/src/export.rs b/src/export.rs
index b97cfc8b..ae12fa1e 100644
--- a/src/export.rs
+++ b/src/export.rs
@@ -1,6 +1,6 @@
 use crate::{Formatter, Str};
 
-#[cfg(target_arch = "x86_64")]
+#[cfg(feature = "unstable-test")]
 thread_local! {
     static I: core::sync::atomic::AtomicU8 =
         core::sync::atomic::AtomicU8::new(0);
@@ -11,23 +11,23 @@ thread_local! {
 // NOTE we limit these values to 7-bit to avoid LEB128 encoding while writing the expected answers
 // in unit tests
 /// For testing purposes
-#[cfg(target_arch = "x86_64")]
+#[cfg(feature = "unstable-test")]
 pub fn fetch_string_index() -> u8 {
     I.with(|i| i.load(core::sync::atomic::Ordering::Relaxed)) & 0x7f
 }
 
 /// For testing purposes
-#[cfg(target_arch = "x86_64")]
+#[cfg(feature = "unstable-test")]
 pub fn fetch_add_string_index() -> usize {
     (I.with(|i| i.fetch_add(1, core::sync::atomic::Ordering::Relaxed)) & 0x7f) as usize
 }
 
-#[cfg(target_arch = "x86_64")]
+#[cfg(feature = "unstable-test")]
 pub fn acquire() -> Option<Formatter> {
     None
 }
 
-#[cfg(not(target_arch = "x86_64"))]
+#[cfg(not(feature = "unstable-test"))]
 #[inline(never)]
 pub fn acquire() -> Option<Formatter> {
     extern "Rust" {
@@ -36,10 +36,10 @@ pub fn acquire() -> Option<Formatter> {
     unsafe { _defmt_acquire() }
 }
 
-#[cfg(target_arch = "x86_64")]
+#[cfg(feature = "unstable-test")]
 pub fn release(_: Formatter) {}
 
-#[cfg(not(target_arch = "x86_64"))]
+#[cfg(not(feature = "unstable-test"))]
 #[inline(never)]
 pub fn release(fmt: Formatter) {
     extern "Rust" {
@@ -49,12 +49,12 @@ pub fn release(fmt: Formatter) {
 }
 
 /// For testing purposes
-#[cfg(target_arch = "x86_64")]
+#[cfg(feature = "unstable-test")]
 pub fn timestamp() -> u64 {
     (T.with(|i| i.fetch_add(1, core::sync::atomic::Ordering::Relaxed)) & 0x7f) as u64
 }
 
-#[cfg(not(target_arch = "x86_64"))]
+#[cfg(not(feature = "unstable-test"))]
 pub fn timestamp() -> u64 {
     extern "Rust" {
         fn _defmt_timestamp() -> u64;
@@ -191,12 +191,12 @@ pub fn into_result<T: sealed::IntoResult>(x: T) -> Result<T::Ok, T::Error> {
 }
 
 /// For testing purposes
-#[cfg(target_arch = "x86_64")]
+#[cfg(feature = "unstable-test")]
 pub fn panic() -> ! {
     panic!()
 }
 
-#[cfg(not(target_arch = "x86_64"))]
+#[cfg(not(feature = "unstable-test"))]
 pub fn panic() -> ! {
     extern "Rust" {
         fn _defmt_panic() -> !;
diff --git a/src/impls.rs b/src/impls.rs
index 58154dea..40b87f49 100644
--- a/src/impls.rs
+++ b/src/impls.rs
@@ -1,4 +1,4 @@
-#[cfg(target_arch = "x86_64")]
+#[cfg(feature = "unstable-test")]
 use crate as defmt;
 use defmt_macros::internp;
 
diff --git a/src/lib.rs b/src/lib.rs
index 6669bd9a..a5abe336 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -10,7 +10,7 @@
 //! with an incompatible version will result in an error. This means that you have to update both
 //! the host and target side if a breaking change in defmt is released.
 
-#![cfg_attr(not(target_arch = "x86_64"), no_std)]
+#![cfg_attr(not(feature = "unstable-test"), no_std)]
 #![warn(missing_docs)]
 
 #[cfg(feature = "alloc")]
@@ -304,9 +304,9 @@ pub struct Str {
 
 /// Handle to a defmt logger.
 pub struct Formatter {
-    #[cfg(not(target_arch = "x86_64"))]
+    #[cfg(not(feature = "unstable-test"))]
     writer: NonNull<dyn Write>,
-    #[cfg(target_arch = "x86_64")]
+    #[cfg(feature = "unstable-test")]
     bytes: Vec<u8>,
     bool_flags: u8, // the current group of consecutive bools
     bools_left: u8, // the number of bits that we can still set in bool_flag
@@ -326,8 +326,8 @@ const MAX_NUM_BOOL_FLAGS: u8 = 8;
 
 #[doc(hidden)]
 impl Formatter {
-    /// Only for testing on x86_64
-    #[cfg(target_arch = "x86_64")]
+    /// Only for testing
+    #[cfg(feature = "unstable-test")]
     pub fn new() -> Self {
         Self {
             bytes: vec![],
@@ -338,24 +338,24 @@ impl Formatter {
         }
     }
 
-    /// Only for testing on x86_64
-    #[cfg(target_arch = "x86_64")]
+    /// Only for testing
+    #[cfg(feature = "unstable-test")]
     pub fn bytes(&self) -> &[u8] {
         &self.bytes
     }
 
-    #[cfg(target_arch = "x86_64")]
+    #[cfg(feature = "unstable-test")]
     pub fn write(&mut self, bytes: &[u8]) {
         self.bytes.extend_from_slice(bytes)
     }
 
-    #[cfg(not(target_arch = "x86_64"))]
+    #[cfg(not(feature = "unstable-test"))]
     pub fn write(&mut self, bytes: &[u8]) {
         unsafe { self.writer.as_mut().write(bytes) }
     }
 
     /// Implementation detail
-    #[cfg(not(target_arch = "x86_64"))]
+    #[cfg(not(feature = "unstable-test"))]
     pub unsafe fn from_raw(writer: NonNull<dyn Write>) -> Self {
         Self {
             writer,
@@ -367,7 +367,7 @@ impl Formatter {
     }
 
     /// Implementation detail
-    #[cfg(not(target_arch = "x86_64"))]
+    #[cfg(not(feature = "unstable-test"))]
     pub unsafe fn into_raw(self) -> NonNull<dyn Write> {
         self.writer
     }
@@ -574,8 +574,8 @@ impl Formatter {
 // these need to be in a separate module or `unreachable!` will end up calling `defmt::panic` and
 // this will not compile
 // (using `core::unreachable!` instead of `unreachable!` doesn't help)
-#[cfg(target_arch = "x86_64")]
-mod x86_64 {
+#[cfg(feature = "unstable-test")]
+mod test_only {
     use core::ptr::NonNull;
 
     use super::Write;
diff --git a/tests/encode.rs b/tests/encode.rs
index 56de8a30..e3e90e9e 100644
--- a/tests/encode.rs
+++ b/tests/encode.rs
@@ -2,7 +2,7 @@
 // depend on `defmt` and `defmt` depends on `defmt-macros` -- the circular dependency may get in
 // the way of `cargo test`
 
-// NOTE string interning is mocked on x86 to aid testing so it does not do real interning. Instead
+// NOTE string interning is mocked when testing so that it does not do real interning. Instead
 // the "interner" always returns a **7-bit** `u8` value that's bumped on every interning operation.
 //
 // In practice, this means that the following operation:
@@ -35,8 +35,6 @@
 // Additional notes:
 //
 // - the mocked index is 7 bits so its LEB128 encoding is the input byte
-// - the family of `info!` macros do nothing on x86; instead use `write!` which takes a formatter
-//   argument
 
 use defmt::{export::fetch_string_index, write, Format, Formatter};