diff --git a/src/tools/miri/Cargo.toml b/src/tools/miri/Cargo.toml
index df987bd3ac6..3da751c69a9 100644
--- a/src/tools/miri/Cargo.toml
+++ b/src/tools/miri/Cargo.toml
@@ -28,8 +28,9 @@ measureme = "10.0.0"
 ctrlc = "3.2.5"
 
 # Copied from `compiler/rustc/Cargo.toml`.
-# But only for Unix, it fails on Windows.
-[target.'cfg(unix)'.dependencies.jemalloc-sys]
+# But only for some targets, it fails for others. Rustc configures this in its CI, but we can't
+# easily use that since we support of-tree builds.
+[target.'cfg(any(target_os = "linux", target_os = "macos"))'.dependencies.jemalloc-sys]
 version = "0.5.0"
 features = ['unprefixed_malloc_on_supported_platforms']
 
diff --git a/src/tools/miri/src/bin/miri.rs b/src/tools/miri/src/bin/miri.rs
index d07753d34df..aead55a6996 100644
--- a/src/tools/miri/src/bin/miri.rs
+++ b/src/tools/miri/src/bin/miri.rs
@@ -298,7 +298,7 @@ fn parse_comma_list<T: FromStr>(input: &str) -> Result<Vec<T>, T::Err> {
     input.split(',').map(str::parse::<T>).collect()
 }
 
-#[cfg(unix)]
+#[cfg(any(target_os = "linux", target_os = "macos"))]
 fn jemalloc_magic() {
     // These magic runes are copied from
     // <https://github.com/rust-lang/rust/blob/e89bd9428f621545c979c0ec686addc6563a394e/compiler/rustc/src/main.rs#L39>.
@@ -335,7 +335,7 @@ fn jemalloc_magic() {
 }
 
 fn main() {
-    #[cfg(unix)]
+    #[cfg(any(target_os = "linux", target_os = "macos"))]
     jemalloc_magic();
 
     let early_dcx = EarlyDiagCtxt::new(ErrorOutputType::default());