diff --git a/docs/functions.rst b/docs/functions.rst
index b0f9e6fc5..effb641a7 100644
--- a/docs/functions.rst
+++ b/docs/functions.rst
@@ -117,7 +117,8 @@ Yet others are handy, general-purpose utilities.
       :arg int fd:
           Write to file descriptor.
       :arg stream:
-          Write to existing stream, which must have methods .write(text) and .flush().
+          Write to existing stream, which must have methods `.write(text)` and
+          `.flush()`.
       :arg str path:
           Write to a file.
       :arg str path_append:
diff --git a/scripts/test.py b/scripts/test.py
index 8e876cdfe..74b32448a 100755
--- a/scripts/test.py
+++ b/scripts/test.py
@@ -97,6 +97,8 @@
     --valgrind 0|1
         Use valgrind in `test` or `buildtest`.
         This will run `sudo apt update` and `sudo apt install valgrind`.
+    --valgrind-args <valgrind_args>
+        Extra args to valgrind.
 
 Commands:
     build
@@ -145,6 +147,7 @@ def main(argv):
 
     build_isolation = None
     valgrind = False
+    valgrind_args = ''
     s = True
     build_do = 'i'
     build_type = None
@@ -216,6 +219,8 @@ def main(argv):
             gdb = int(next(args))
         elif arg == '--valgrind':
             valgrind = int(next(args))
+        elif arg == '--valgrind-args':
+            valgrind_args = next(args)
         else:
             assert 0, f'Unrecognised option: {arg=}.'
     
@@ -259,6 +264,7 @@ def do_test():
         test(
                 implementations=implementations,
                 valgrind=valgrind,
+                valgrind_args=valgrind_args,
                 venv_quick=venv_quick,
                 test_names=test_names,
                 pytest_options=pytest_options,
@@ -586,6 +592,7 @@ def write( text, path):
 def test(
         implementations,
         valgrind,
+        valgrind_args,
         venv_quick=False,
         test_names=None,
         pytest_options=None,
@@ -600,6 +607,8 @@ def test(
             See top-level option `-i`.
         valgrind:
             See top-level option `--valgrind`.
+        valgrind_args:
+            See top-level option `--valgrind-args`.
         venv_quick:
             .
         test_names:
@@ -647,7 +656,7 @@ def test(
             log('Running PyMuPDF tests under valgrind.')
             command = (
                     f'{python} {pymupdf_dir_rel}/tests/run_compound.py{run_compound_args}'
-                        f' valgrind --suppressions={pymupdf_dir_rel}/valgrind.supp --error-exitcode=100 --errors-for-leak-kinds=none --fullpath-after='
+                        f' valgrind --suppressions={pymupdf_dir_rel}/valgrind.supp --error-exitcode=100 --errors-for-leak-kinds=none --fullpath-after= {valgrind_args}'
                         f' {python} -m pytest {pytest_options}{pytest_arg}'
                         )
             env_extra=dict(
diff --git a/setup.py b/setup.py
index a1c0d601d..a0056433b 100755
--- a/setup.py
+++ b/setup.py
@@ -658,17 +658,22 @@ def add(flavour, from_, to_):
             add('b', pipcl.get_soname(f'{mupdf_build_dir}/libmupdf.so'), to_dir)
 
         if 'd' in PYMUPDF_SETUP_FLAVOUR:
-            # Add MuPDF headers to `ret_d`. Would prefer to use
+            # Add MuPDF C and C++ headers to `ret_d`. Would prefer to use
             # pipcl.git_items() but hard-coded mupdf tree is not a git
             # checkout.
             #
-            include = f'{mupdf_local}/include'
-            for dirpath, dirnames, filenames in os.walk(include):
-                for filename in filenames:
-                    header_abs = os.path.join(dirpath, filename)
-                    assert header_abs.startswith(include)
-                    header_rel = header_abs[len(include)+1:]
-                    add('d', f'{header_abs}', f'{to_dir_d}/include/{header_rel}')
+            for root in (
+                    f'{mupdf_local}/include',
+                    f'{mupdf_local}/platform/c++/include',
+                    ):
+                for dirpath, dirnames, filenames in os.walk(root):
+                    for filename in filenames:
+                        if not filename.endswith('.h'):
+                            continue
+                        header_abs = os.path.join(dirpath, filename)
+                        assert header_abs.startswith(root)
+                        header_rel = header_abs[len(root)+1:]
+                        add('d', f'{header_abs}', f'{to_dir_d}/include/{header_rel}')
     
     # Add a .py file containing location of MuPDF.
     text = f"mupdf_location='{mupdf_location}'\n"
diff --git a/src/__init__.py b/src/__init__.py
index 24a819494..3002f34ef 100644
--- a/src/__init__.py
+++ b/src/__init__.py
@@ -117,7 +117,7 @@ def _make_output(
                 pylogging_level = int(pylogging_level)
             pylogging_name = items_d.get('name', 'pymupdf')
         else:
-            assert 0, f'Unrecognised {text=}.'
+            assert 0, f'Expected prefix `fd:`, `path:`. `path+:` or `logging:` in {text=}.'
     
     if fd is not None:
         ret = open(fd, mode='w', closefd=False)
@@ -154,10 +154,8 @@ def write(self, text):
             def flush(self):
                 pass
         ret = Out()
-    elif default:
-        ret = default
     else:
-        assert 0, f'No output specified.'
+        ret = default
     return ret
 
 # Set steam used by PyMuPDF messaging.
@@ -259,14 +257,18 @@ def log( text='', caller=1):
         text = f'{filename}:{line}:{function}(): {text}'
     if _g_log_items_active:
         _g_log_items.append(text)
-    print(text, file=_g_out_log, flush=1)
+    if _g_out_log:
+        print(text, file=_g_out_log, flush=1)
 
 
 def message(text=''):
     '''
     For user messages.
     '''
-    print(text, file=_g_out_message, flush=1)
+    # It looks like `print()` does nothing if sys.stdout is None (without
+    # raising an exception), but we don't rely on this.
+    if _g_out_message:
+        print(text, file=_g_out_message, flush=1)
 
 
 def exception_info():
diff --git a/tests/test_annots.py b/tests/test_annots.py
index ea9aa07bc..8fe7b54d4 100644
--- a/tests/test_annots.py
+++ b/tests/test_annots.py
@@ -419,3 +419,23 @@ def test_3863():
             # We get small differences in sysinstall tests, where some
             # thirdparty libraries can differ.
             assert rms < 1
+
+def test_3758():
+    # This test requires input file that is not public, so is usually not
+    # available.
+    path = os.path.normpath(f'{__file__}/../../../test_3758.pdf')
+    if not os.path.exists(path):
+        print(f'test_3758(): not running because does not exist: {path=}.')
+        return
+    import json
+    with pymupdf.open(path) as document:
+        for page in document:
+            info = json.loads(page.get_text('json', flags=pymupdf.TEXTFLAGS_TEXT))
+            for block_ind, block in enumerate(info['blocks']):
+                for line_ind, line in enumerate(block['lines']):
+                    for span_ind, span in enumerate(line['spans']):
+                        # print(span)
+                        page.add_redact_annot(pymupdf.Rect(*span['bbox']))
+            page.apply_redactions()
+    wt = pymupdf.TOOLS.mupdf_warnings()
+    assert wt
diff --git a/tests/test_general.py b/tests/test_general.py
index b766fb04d..2d87f22c4 100644
--- a/tests/test_general.py
+++ b/tests/test_general.py
@@ -1283,6 +1283,20 @@ def check(
             ],
             )
     
+    print(f'## Check messages() with sys.stdout=None.')
+    check(
+            '''
+            import sys
+            sys.stdout = None
+            import pymupdf
+            
+            pymupdf.message('this is pymupdf.message()')
+            pymupdf.log('this is pymupdf.log()')
+            ''',
+            [],
+            [],
+            )
+    
 
 def relpath(path, start=None):
     '''