diff --git a/tests/testsuite/mock-std/library/compiler_builtins/src/lib.rs b/tests/testsuite/mock-std/library/compiler_builtins/src/lib.rs
index 65e2cc34045..0c9ac1ac8e4 100644
--- a/tests/testsuite/mock-std/library/compiler_builtins/src/lib.rs
+++ b/tests/testsuite/mock-std/library/compiler_builtins/src/lib.rs
@@ -1 +1 @@
-// intentionally blank
+#![no_std]
diff --git a/tests/testsuite/mock-std/library/core/src/lib.rs b/tests/testsuite/mock-std/library/core/src/lib.rs
index b90ed091414..fd317cb1d69 100644
--- a/tests/testsuite/mock-std/library/core/src/lib.rs
+++ b/tests/testsuite/mock-std/library/core/src/lib.rs
@@ -1,3 +1,4 @@
+#![no_std]
 #![feature(staged_api)]
 #![stable(since = "1.0.0", feature = "dummy")]
 
diff --git a/tests/testsuite/standard_lib.rs b/tests/testsuite/standard_lib.rs
index afcc79f750b..214df036561 100644
--- a/tests/testsuite/standard_lib.rs
+++ b/tests/testsuite/standard_lib.rs
@@ -395,12 +395,13 @@ fn test_std_on_unsupported_target() {
 
     let p = project()
         .file(
-            "src/main.rs",
+            "src/lib.rs",
             r#"
-        fn main() {
-            println!("hello");
-        }
-        "#,
+                #![no_std]
+                pub fn foo() {
+                    assert_eq!(u8::MIN, 0);
+                }
+            "#,
         )
         .build();