diff --git a/tests/fail/unsized-local.rs b/tests/fail/unsized-local.rs
new file mode 100644
index 000000000000..8dd07c585c62
--- /dev/null
+++ b/tests/fail/unsized-local.rs
@@ -0,0 +1,23 @@
+#![feature(unsized_locals)]
+#![allow(incomplete_features)]
+
+fn main() {
+    pub trait Foo {
+        fn foo(self) -> String;
+    }
+
+    struct A;
+
+    impl Foo for A {
+        fn foo(self) -> String {
+            format!("hello")
+        }
+    }
+
+    let x = *(Box::new(A) as Box<dyn Foo>); //~ERROR unsized locals are not supported
+    assert_eq!(x.foo(), format!("hello"));
+
+    // I'm not sure whether we want this to work
+    let x = Box::new(A) as Box<dyn Foo>;
+    assert_eq!(x.foo(), format!("hello"));
+}
diff --git a/tests/fail/unsized-local.stderr b/tests/fail/unsized-local.stderr
new file mode 100644
index 000000000000..8277bc4546cb
--- /dev/null
+++ b/tests/fail/unsized-local.stderr
@@ -0,0 +1,14 @@
+error: unsupported operation: unsized locals are not supported
+  --> $DIR/unsized-local.rs:LL:CC
+   |
+LL |     let x = *(Box::new(A) as Box<dyn Foo>);
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ unsized locals are not supported
+   |
+   = help: this is likely not a bug in the program; it indicates that the program performed an operation that the interpreter does not support
+   = note: backtrace:
+   = note: inside `main` at $DIR/unsized-local.rs:LL:CC
+
+note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
+
+error: aborting due to previous error
+
diff --git a/tests/pass/dyn-traits.rs b/tests/pass/dyn-traits.rs
index 00667757b048..908d521a0d81 100644
--- a/tests/pass/dyn-traits.rs
+++ b/tests/pass/dyn-traits.rs
@@ -1,6 +1,3 @@
-#![feature(unsized_locals, unsized_fn_params)]
-#![allow(incomplete_features)]
-
 fn ref_box_dyn() {
     struct Struct(i32);
 
@@ -75,6 +72,9 @@ fn box_box_trait() {
     assert!(unsafe { DROPPED });
 }
 
+// Disabled for now: unsized locals are not supported,
+// their current MIR encoding is just not great.
+/*
 fn unsized_dyn() {
     pub trait Foo {
         fn foo(self) -> String;
@@ -95,7 +95,6 @@ fn unsized_dyn() {
     let x = Box::new(A) as Box<dyn Foo>;
     assert_eq!(x.foo(), format!("hello"));
 }
-
 fn unsized_dyn_autoderef() {
     pub trait Foo {
         fn foo(self) -> String;
@@ -140,12 +139,9 @@ fn unsized_dyn_autoderef() {
     let x = Box::new(|| "hello".to_owned()) as Box<dyn FnMut() -> String>;
     assert_eq!(&x.foo() as &str, "hello");
 }
+*/
 
 fn main() {
     ref_box_dyn();
     box_box_trait();
-
-    // "exotic" receivers
-    unsized_dyn();
-    unsized_dyn_autoderef();
 }
diff --git a/tests/pass/unsized-tuple-impls.rs b/tests/pass/unsized-tuple-impls.rs
deleted file mode 100644
index bbab1125a0af..000000000000
--- a/tests/pass/unsized-tuple-impls.rs
+++ /dev/null
@@ -1,13 +0,0 @@
-#![feature(unsized_tuple_coercion)]
-use std::mem;
-
-fn main() {
-    let x: &(i32, i32, [i32]) = &(0, 1, [2, 3]);
-    let y: &(i32, i32, [i32]) = &(0, 1, [2, 3, 4]);
-    let mut a = [y, x];
-    a.sort();
-    assert_eq!(a, [x, y]);
-
-    assert_eq!(&format!("{:?}", a), "[(0, 1, [2, 3]), (0, 1, [2, 3, 4])]");
-    assert_eq!(mem::size_of_val(x), 16);
-}
diff --git a/tests/pass/unsized.rs b/tests/pass/unsized.rs
new file mode 100644
index 000000000000..c7e0c7925753
--- /dev/null
+++ b/tests/pass/unsized.rs
@@ -0,0 +1,36 @@
+#![feature(unsized_tuple_coercion)]
+#![feature(unsized_fn_params)]
+
+use std::mem;
+
+fn unsized_tuple() {
+    let x: &(i32, i32, [i32]) = &(0, 1, [2, 3]);
+    let y: &(i32, i32, [i32]) = &(0, 1, [2, 3, 4]);
+    let mut a = [y, x];
+    a.sort();
+    assert_eq!(a, [x, y]);
+
+    assert_eq!(&format!("{:?}", a), "[(0, 1, [2, 3]), (0, 1, [2, 3, 4])]");
+    assert_eq!(mem::size_of_val(x), 16);
+}
+
+fn unsized_params() {
+    pub fn f0(_f: dyn FnOnce()) {}
+    pub fn f1(_s: str) {}
+    pub fn f2(_x: i32, _y: [i32]) {}
+    pub fn f3(_p: dyn Send) {}
+
+    let c: Box<dyn FnOnce()> = Box::new(|| {});
+    f0(*c);
+    let foo = "foo".to_string().into_boxed_str();
+    f1(*foo);
+    let sl: Box::<[i32]> = [0, 1, 2].to_vec().into_boxed_slice();
+    f2(5, *sl);
+    let p: Box<dyn Send> = Box::new((1, 2));
+    f3(*p);
+}
+
+fn main() {
+    unsized_tuple();
+    unsized_params();
+}