diff --git a/src/nvim/os/env.c b/src/nvim/os/env.c
index 3126881266..21da64a1ee 100644
--- a/src/nvim/os/env.c
+++ b/src/nvim/os/env.c
@@ -127,9 +127,6 @@ bool os_env_exists(const char *name)
 /// Sets an environment variable.
 ///
 /// Windows (Vim-compat): Empty string (:let $FOO="") undefines the env var.
-///
-/// @warning Existing pointers to the result of os_getenv("foo") are
-///          INVALID after os_setenv("foo", …).
 int os_setenv(const char *name, const char *value, int overwrite)
   FUNC_ATTR_NONNULL_ALL
 {
diff --git a/src/nvim/tui/tui.c b/src/nvim/tui/tui.c
index bb91b5336a..91bb65898c 100644
--- a/src/nvim/tui/tui.c
+++ b/src/nvim/tui/tui.c
@@ -387,10 +387,12 @@ static void terminfo_start(TUIData *tui)
 
   const char *term = os_getenv("TERM");
 #ifdef MSWIN
-  os_tty_guess_term(&term, tui->out_fd);
-  os_setenv("TERM", term, 1);
-  // Old os_getenv() pointer is invalid after os_setenv(), fetch it again.
-  term = os_getenv("TERM");
+  const char *guessed_term = NULL;
+  os_tty_guess_term(&guessed_term, tui->out_fd);
+  if (term == NULL && guessed_term != NULL) {
+    term = xstrdup(guessed_term);
+    os_setenv("TERM", guessed_term, 1);
+  }
 #endif
 
   // Set up unibilium/terminfo.