diff --git a/src/misc1.c b/src/misc1.c
index af83c10..9aa8ecf 100644
--- a/src/misc1.c
+++ b/src/misc1.c
@@ -1910,6 +1910,20 @@
 #endif
 }
 
+/*
+ * Removes environment variable "name" and take care of side effects.
+ */
+    void
+vim_unsetenv_ext(char_u *var)
+{
+    vim_unsetenv(var);
+
+    // "homedir" is not cleared, keep using the old value until $HOME is set.
+    if (STRICMP(var, "VIM") == 0)
+	didset_vim = FALSE;
+    else if (STRICMP(var, "VIMRUNTIME") == 0)
+	didset_vimruntime = FALSE;
+}
 
 /*
  * Set environment variable "name" and take care of side effects.
@@ -1922,8 +1936,7 @@
 	init_homedir();
     else if (didset_vim && STRICMP(name, "VIM") == 0)
 	didset_vim = FALSE;
-    else if (didset_vimruntime
-	    && STRICMP(name, "VIMRUNTIME") == 0)
+    else if (didset_vimruntime && STRICMP(name, "VIMRUNTIME") == 0)
 	didset_vimruntime = FALSE;
 }
 #endif