diff --git a/src/liballoc/tests/binary_heap.rs b/src/liballoc/tests/binary_heap.rs
index a44cf1eaf6df0..a896a1064d9e1 100644
--- a/src/liballoc/tests/binary_heap.rs
+++ b/src/liballoc/tests/binary_heap.rs
@@ -347,7 +347,7 @@ fn assert_covariance() {
 // Destructors must be called exactly once per element.
 // FIXME: re-enable emscripten once it can unwind again
 #[test]
-#[cfg(not(any(miri, target_os = "emscripten")))] // Miri does not support catching panics
+#[cfg(not(target_os = "emscripten"))]
 fn panic_safe() {
     use std::cmp;
     use std::panic::{self, AssertUnwindSafe};
@@ -376,7 +376,10 @@ fn panic_safe() {
     }
     let mut rng = thread_rng();
     const DATASZ: usize = 32;
+    #[cfg(not(miri))] // Miri is too slow
     const NTEST: usize = 10;
+    #[cfg(miri)]
+    const NTEST: usize = 1;
 
     // don't use 0 in the data -- we want to catch the zeroed-out case.
     let data = (1..=DATASZ).collect::<Vec<_>>();
diff --git a/src/liballoc/tests/slice.rs b/src/liballoc/tests/slice.rs
index ad2cd7c95eb8f..d9707b9574078 100644
--- a/src/liballoc/tests/slice.rs
+++ b/src/liballoc/tests/slice.rs
@@ -4,7 +4,6 @@ use std::mem;
 use std::panic;
 use std::rc::Rc;
 use std::sync::atomic::{Ordering::Relaxed, AtomicUsize};
-use std::thread;
 
 use rand::{Rng, RngCore, thread_rng};
 use rand::seq::SliceRandom;
@@ -1406,11 +1405,9 @@ fn test_box_slice_clone() {
 #[test]
 #[allow(unused_must_use)] // here, we care about the side effects of `.clone()`
 #[cfg_attr(target_os = "emscripten", ignore)]
-#[cfg(not(miri))] // Miri does not support threads
 fn test_box_slice_clone_panics() {
     use std::sync::Arc;
     use std::sync::atomic::{AtomicUsize, Ordering};
-    use std::thread::spawn;
 
     struct Canary {
         count: Arc<AtomicUsize>,
@@ -1446,7 +1443,7 @@ fn test_box_slice_clone_panics() {
         panics: true,
     };
 
-    spawn(move || {
+    std::panic::catch_unwind(move || {
             // When xs is dropped, +5.
             let xs = vec![canary.clone(), canary.clone(), canary.clone(), panic, canary]
                 .into_boxed_slice();
@@ -1454,7 +1451,6 @@ fn test_box_slice_clone_panics() {
             // When panic is cloned, +3.
             xs.clone();
         })
-        .join()
         .unwrap_err();
 
     // Total = 8
@@ -1566,7 +1562,7 @@ macro_rules! test {
             }
 
             let v = $input.to_owned();
-            let _ = thread::spawn(move || {
+            let _ = std::panic::catch_unwind(move || {
                 let mut v = v;
                 let mut panic_countdown = panic_countdown;
                 v.$func(|a, b| {
@@ -1577,7 +1573,7 @@ macro_rules! test {
                     panic_countdown -= 1;
                     a.cmp(b)
                 })
-            }).join();
+            });
 
             // Check that the number of things dropped is exactly
             // what we expect (i.e., the contents of `v`).
@@ -1598,7 +1594,6 @@ thread_local!(static SILENCE_PANIC: Cell<bool> = Cell::new(false));
 
 #[test]
 #[cfg_attr(target_os = "emscripten", ignore)] // no threads
-#[cfg(not(miri))] // Miri does not support threads
 fn panic_safe() {
     let prev = panic::take_hook();
     panic::set_hook(Box::new(move |info| {
@@ -1609,8 +1604,18 @@ fn panic_safe() {
 
     let mut rng = thread_rng();
 
-    for len in (1..20).chain(70..MAX_LEN) {
-        for &modulus in &[5, 20, 50] {
+    #[cfg(not(miri))] // Miri is too slow
+    let lens = (1..20).chain(70..MAX_LEN);
+    #[cfg(not(miri))] // Miri is too slow
+    let moduli = &[5, 20, 50];
+
+    #[cfg(miri)]
+    let lens = (1..13);
+    #[cfg(miri)]
+    let moduli = &[10];
+
+    for len in lens {
+        for &modulus in moduli {
             for &has_runs in &[false, true] {
                 let mut input = (0..len)
                     .map(|id| {
@@ -1643,6 +1648,9 @@ fn panic_safe() {
             }
         }
     }
+
+    // Set default panic hook again.
+    drop(panic::take_hook());
 }
 
 #[test]
diff --git a/src/liballoc/tests/vec.rs b/src/liballoc/tests/vec.rs
index 0cc8da096f395..9ee254f99acdf 100644
--- a/src/liballoc/tests/vec.rs
+++ b/src/liballoc/tests/vec.rs
@@ -944,10 +944,9 @@ fn drain_filter_complex() {
     }
 }
 
-// Miri does not support catching panics
 // FIXME: re-enable emscripten once it can unwind again
 #[test]
-#[cfg(not(any(miri, target_os = "emscripten")))]
+#[cfg(not(target_os = "emscripten"))]
 fn drain_filter_consumed_panic() {
     use std::rc::Rc;
     use std::sync::Mutex;
@@ -999,7 +998,7 @@ fn drain_filter_consumed_panic() {
 
 // FIXME: Re-enable emscripten once it can catch panics
 #[test]
-#[cfg(not(any(miri, target_os = "emscripten")))] // Miri does not support catching panics
+#[cfg(not(target_os = "emscripten"))]
 fn drain_filter_unconsumed_panic() {
     use std::rc::Rc;
     use std::sync::Mutex;