diff --git a/tests/compile-fail/ctlz_nonzero.rs b/tests/compile-fail/ctlz_nonzero.rs
index 4e2ccd0ac508..86fd5ec46c20 100644
--- a/tests/compile-fail/ctlz_nonzero.rs
+++ b/tests/compile-fail/ctlz_nonzero.rs
@@ -8,7 +8,7 @@ mod rusti {
 
 pub fn main() {
     unsafe {
-        use rusti::*;
+        use crate::rusti::*;
 
         ctlz_nonzero(0u8); //~ ERROR constant evaluation error: ctlz_nonzero called on 0
     }
diff --git a/tests/compile-fail/cttz_nonzero.rs b/tests/compile-fail/cttz_nonzero.rs
index 50b8df619982..a6c3b03cfb5c 100644
--- a/tests/compile-fail/cttz_nonzero.rs
+++ b/tests/compile-fail/cttz_nonzero.rs
@@ -8,7 +8,7 @@ mod rusti {
 
 pub fn main() {
     unsafe {
-        use rusti::*;
+        use crate::rusti::*;
 
         cttz_nonzero(0u8); //~ ERROR constant evaluation error: cttz_nonzero called on 0
     }
diff --git a/tests/compiletest.rs b/tests/compiletest.rs
index 7ecf64590b61..7aa55ef66340 100644
--- a/tests/compiletest.rs
+++ b/tests/compiletest.rs
@@ -62,6 +62,7 @@ fn compile_fail(sysroot: &Path, path: &str, target: &str, host: &str, need_fullm
     let mut flags = Vec::new();
     flags.push(format!("--sysroot {}", sysroot.display()));
     flags.push("-Dwarnings -Dunused".to_owned()); // overwrite the -Aunused in compiletest-rs
+    flags.push("--edition 2018".to_owned());
     if opt {
         // Optimizing too aggressivley makes UB detection harder, but test at least
         // the default value.
@@ -98,6 +99,7 @@ fn miri_pass(sysroot: &Path, path: &str, target: &str, host: &str, need_fullmir:
     let mut flags = Vec::new();
     flags.push(format!("--sysroot {}", sysroot.display()));
     flags.push("-Dwarnings -Dunused".to_owned()); // overwrite the -Aunused in compiletest-rs
+    flags.push("--edition 2018".to_owned());
     if opt {
         // FIXME: We use opt level 1 because MIR inlining defeats the validation
         // whitelist.
diff --git a/tests/run-pass-fullmir/foreign-fn-linkname.rs b/tests/run-pass-fullmir/foreign-fn-linkname.rs
index 789e3eccceb7..b61cfa84ef75 100644
--- a/tests/run-pass-fullmir/foreign-fn-linkname.rs
+++ b/tests/run-pass-fullmir/foreign-fn-linkname.rs
@@ -9,14 +9,16 @@
 // except according to those terms.
 
 //ignore-windows: Uses POSIX APIs
-#![feature(libc)]
+
+#![feature(libc, extern_crate_item_prelude)]
+#![allow(unused_extern_crates)] // rustc bug https://github.com/rust-lang/rust/issues/56098
 
 extern crate libc;
+
 use std::ffi::CString;
 
 mod mlibc {
     use libc::{c_char, size_t};
-
     extern {
         #[link_name = "strlen"]
         pub fn my_strlen(str: *const c_char) -> size_t;
diff --git a/tests/run-pass-fullmir/memchr.rs b/tests/run-pass-fullmir/memchr.rs
index 36eb85dcf7e8..2f5e2c4bb739 100644
--- a/tests/run-pass-fullmir/memchr.rs
+++ b/tests/run-pass-fullmir/memchr.rs
@@ -1,6 +1,5 @@
 #![feature(slice_internals)]
 
-extern crate core;
 use core::slice::memchr::{memchr, memrchr};
 
 // test fallback implementations on all platforms
diff --git a/tests/run-pass/intrinsics-integer.rs b/tests/run-pass/intrinsics-integer.rs
index 4896f02da20b..de59314eff5a 100644
--- a/tests/run-pass/intrinsics-integer.rs
+++ b/tests/run-pass/intrinsics-integer.rs
@@ -23,7 +23,7 @@ mod rusti {
 
 pub fn main() {
     unsafe {
-        use rusti::*;
+        use crate::rusti::*;
 
         assert_eq!(ctpop(0u8), 0); assert_eq!(ctpop(0i8), 0);
         assert_eq!(ctpop(0u16), 0); assert_eq!(ctpop(0i16), 0);
diff --git a/tests/run-pass/stacked-borrows.rs b/tests/run-pass/stacked-borrows.rs
index 7b7a7c9be203..72f26763be14 100644
--- a/tests/run-pass/stacked-borrows.rs
+++ b/tests/run-pass/stacked-borrows.rs
@@ -68,13 +68,11 @@ fn mut_shr_raw() {
 // That should work.
 fn mut_raw_then_mut_shr() {
     let mut x = 2;
-    {
-        let xref = &mut x;
-        let xraw = &mut *xref as *mut _;
-        let xshr = &*xref;
-        assert_eq!(*xshr, 2);
-        unsafe { *xraw = 4; }
-    }
+    let xref = &mut x;
+    let xraw = &mut *xref as *mut _;
+    let xshr = &*xref;
+    assert_eq!(*xshr, 2);
+    unsafe { *xraw = 4; }
     assert_eq!(x, 4);
 }