diff --git a/lib/spack/llnl/util/tty/log.py b/lib/spack/llnl/util/tty/log.py
index d05bb750115..b89745c60b0 100644
--- a/lib/spack/llnl/util/tty/log.py
+++ b/lib/spack/llnl/util/tty/log.py
@@ -344,26 +344,6 @@ def close(self):
             self.file.close()
 
 
-@contextmanager
-def replace_environment(env):
-    """Replace the current environment (`os.environ`) with `env`.
-
-    If `env` is empty (or None), this unsets all current environment
-    variables.
-    """
-    env = env or {}
-    old_env = os.environ.copy()
-    try:
-        os.environ.clear()
-        for name, val in env.items():
-            os.environ[name] = val
-        yield
-    finally:
-        os.environ.clear()
-        for name, val in old_env.items():
-            os.environ[name] = val
-
-
 def log_output(*args, **kwargs):
     """Context manager that logs its output to a file.
 
@@ -447,7 +427,6 @@ def __init__(
         self.echo = echo
         self.debug = debug
         self.buffer = buffer
-        self.env = env  # the environment to use for _writer_daemon
         self.filter_fn = filter_fn
 
         self._active = False  # used to prevent re-entry
@@ -519,21 +498,20 @@ def __enter__(self):
                 # just don't forward input if this fails
                 pass
 
-            with replace_environment(self.env):
-                self.process = multiprocessing.Process(
-                    target=_writer_daemon,
-                    args=(
-                        input_fd,
-                        read_fd,
-                        self.write_fd,
-                        self.echo,
-                        self.log_file,
-                        child_pipe,
-                        self.filter_fn,
-                    ),
-                )
-                self.process.daemon = True  # must set before start()
-                self.process.start()
+            self.process = multiprocessing.Process(
+                target=_writer_daemon,
+                args=(
+                    input_fd,
+                    read_fd,
+                    self.write_fd,
+                    self.echo,
+                    self.log_file,
+                    child_pipe,
+                    self.filter_fn,
+                ),
+            )
+            self.process.daemon = True  # must set before start()
+            self.process.start()
 
         finally:
             if input_fd:
@@ -729,10 +707,7 @@ class winlog:
     Does not support the use of 'v' toggling as nixlog does.
     """
 
-    def __init__(
-        self, file_like=None, echo=False, debug=0, buffer=False, env=None, filter_fn=None
-    ):
-        self.env = env
+    def __init__(self, file_like=None, echo=False, debug=0, buffer=False, filter_fn=None):
         self.debug = debug
         self.echo = echo
         self.logfile = file_like
@@ -789,11 +764,10 @@ def background_reader(reader, echo_writer, _kill):
                     reader.close()
 
             self._active = True
-            with replace_environment(self.env):
-                self._thread = Thread(
-                    target=background_reader, args=(self.reader, self.echo_writer, self._kill)
-                )
-                self._thread.start()
+            self._thread = Thread(
+                target=background_reader, args=(self.reader, self.echo_writer, self._kill)
+            )
+            self._thread.start()
         return self
 
     def __exit__(self, exc_type, exc_val, exc_tb):
diff --git a/lib/spack/spack/installer.py b/lib/spack/spack/installer.py
index 067fe982c20..37a1301733a 100644
--- a/lib/spack/spack/installer.py
+++ b/lib/spack/spack/installer.py
@@ -2436,11 +2436,7 @@ def _real_install(self) -> None:
                     # DEBUGGING TIP - to debug this section, insert an IPython
                     # embed here, and run the sections below without log capture
                     log_contextmanager = log_output(
-                        log_file,
-                        self.echo,
-                        True,
-                        env=self.unmodified_env,
-                        filter_fn=self.filter_fn,
+                        log_file, self.echo, True, filter_fn=self.filter_fn
                     )
 
                     with log_contextmanager as logger: