diff --git a/changes.txt b/changes.txt
index 11a3335fd..084068c2e 100644
--- a/changes.txt
+++ b/changes.txt
@@ -2,10 +2,12 @@ Change Log
 ==========
 
 
-**Changes in version 1.26.7**
+**Changes in version 1.26.7** (2025-12-11)
 
 * Use MuPDF-1.26.12.
 
+  * **Fixed** `4801 <https://github.com/pymupdf/PyMuPDF/issues/4801>`_: Build failure dumping all environment variables
+
 Other:
 
   * Retrospectively mark `4756 <https://github.com/pymupdf/PyMuPDF/issues/4756>`_ as fixed in 1.26.6.
diff --git a/pipcl.py b/pipcl.py
index c25c5118a..e1cac6979 100644
--- a/pipcl.py
+++ b/pipcl.py
@@ -96,6 +96,7 @@ class Package:
         ...                         name = 'foo',
         ...                         path_i = 'foo.i',
         ...                         outdir = 'build',
+        ...                         source_extra = 'wibble.c',
         ...                         )
         ...                 return [
         ...                         ('build/foo.py', 'foo/__init__.py'),
@@ -107,8 +108,10 @@ class Package:
         ...
         ...             def sdist():
         ...                 return [
+        ...                         'pyproject.toml',
         ...                         'foo.i',
         ...                         'bar.i',
+        ...                         'wibble.c',
         ...                         'setup.py',
         ...                         'pipcl.py',
         ...                         'wdev.py',
@@ -160,6 +163,12 @@ class Package:
         >>> with open('pipcl_test/bar.i', 'w') as f:
         ...     _ = f.write( '\\n')
 
+        >>> with open('pipcl_test/wibble.c', 'w') as f:
+        ...     _ = f.write( '\\n')
+
+        >>> with open('pipcl_test/pyproject.toml', 'w') as f:
+        ...     pass
+
         >>> with open('pipcl_test/README', 'w') as f:
         ...     _ = f.write(textwrap.dedent("""
         ...             This is Foo.
@@ -262,6 +271,19 @@ class Package:
         >>> so = so[0]
         >>> assert os.path.getmtime(so) > t0
 
+    Check that touching wibble.c does not run swig, but does recompile/link.
+
+        >>> t0 = time.time()
+        >>> os.utime('pipcl_test/wibble.c')
+        >>> _ = subprocess.run(
+        ...         f'cd pipcl_test && {sys.executable} setup.py bdist_wheel',
+        ...         shell=1, check=1)
+        >>> assert os.path.getmtime('pipcl_test/build/foo.py') <= t0
+        >>> so = glob.glob('pipcl_test/build/*.so')
+        >>> assert len(so) == 1
+        >>> so = so[0]
+        >>> assert os.path.getmtime(so) > t0
+
     Check `entry_points` causes creation of command `foo_cli` when we install
     from our wheel using pip. [As of 2024-02-24 using pipcl's CLI interface
     directly with `setup.py install` does not support entry points.]
@@ -1802,7 +1824,7 @@ def build_extension(
 
     for path_source in [path_cpp] + source_extra:
         path_o = f'{path_source}.obj' if windows() else f'{path_source}.o'
-        path_os.append(f' {path_o}')
+        path_os.append(path_o)
 
         prerequisites_path = f'{path_o}.d'