RustPython
diff --git a/Lib/test/test_logging.py b/Lib/test/test_logging.py
@@ -4119,8 +4119,6 @@ def test_90195(self):
         # Logger should be enabled, since explicitly mentioned
         self.assertFalse(logger.disabled)
 
-    # TODO: RUSTPYTHON - SemLock not implemented on Windows
-    @unittest.expectedFailureIfWindows("TODO: RUSTPYTHON")
     def test_111615(self):
         # See gh-111615
         import_helper.import_module('_multiprocessing')  # see gh-113692

diff --git a/Lib/test/test_socket.py b/Lib/test/test_socket.py
@@ -6620,7 +6620,6 @@ def remoteProcessServer(cls, q):
         s2.close()
         s.close()
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON; multiprocessing.SemLock not implemented
     def testShare(self):
         # Transfer the listening server socket to another process
         # and service it from there.

diff --git a/crates/stdlib/src/mmap.rs b/crates/stdlib/src/mmap.rs
@@ -557,9 +557,15 @@ mod mmap {
             // Parse tagname: None or a string
             let tag_str: Option<String> = match tagname {
                 Some(ref obj) if !vm.is_none(obj) => {
-                    Some(obj.try_to_value::<String>(vm).map_err(|_| {
+                    let s = obj.try_to_value::<String>(vm).map_err(|_| {
                         vm.new_type_error("tagname must be a string or None".to_owned())
-                    })?)
+                    })?;
+                    if s.contains('\0') {
+                        return Err(vm.new_value_error(
+                            "tagname must not contain null characters".to_owned(),
+                        ));
+                    }
+                    Some(s)
                 }
                 _ => None,
             };