diff --git a/std/src/ffi/os_str.rs b/std/src/ffi/os_str.rs
index 8e1147338b047..0f905803bb8b9 100644
--- a/std/src/ffi/os_str.rs
+++ b/std/src/ffi/os_str.rs
@@ -919,6 +919,7 @@ impl OsStr {
     #[must_use = "this returns the result of the operation, \
                   without modifying the original"]
     #[inline]
+    #[cfg_attr(not(test), rustc_diagnostic_item = "os_str_to_os_string")]
     pub fn to_os_string(&self) -> OsString {
         OsString { inner: self.inner.to_owned() }
     }
diff --git a/std/src/path.rs b/std/src/path.rs
index 6d6aa92711ba4..2ba3a9cdca251 100644
--- a/std/src/path.rs
+++ b/std/src/path.rs
@@ -2265,6 +2265,7 @@ impl Path {
     #[must_use = "this returns the result of the operation, \
                   without modifying the original"]
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[cfg_attr(not(test), rustc_diagnostic_item = "path_to_pathbuf")]
     pub fn to_path_buf(&self) -> PathBuf {
         PathBuf::from(self.inner.to_os_string())
     }