patch 8.0.1832: cannot use :unlet for an environment variable commit https://github.com/vim/vim/commit/137374fd6538cf9dee0cb22907728d8fdecb5832 Author: Bram Moolenaar <Bram@vim.org> Date: Sun May 13 15:59:50 2018 +0200 patch 8.0.1832: cannot use :unlet for an environment variable Problem: Cannot use :unlet for an environment variable. Solution: Make it work. Use unsetenv() if available. (Ken Takata, closes #2855)

--- a/src/misc1.c
+++ b/src/misc1.c
@@ -4479,6 +4479,17 @@ remove_tail(char_u *p, char_u *pend, cha
     return pend;
 }
 
+    void
+vim_unsetenv(char_u *var)
+{
+#ifdef HAVE_UNSETENV
+    unsetenv((char *)var);
+#else
+    mch_setenv((char *)var, "", 0);
+#endif
+}
+
+
 /*
  * Our portable version of setenv.
  */