diff --git a/README.md b/README.md
index 9e00a27d..f88a1972 100644
--- a/README.md
+++ b/README.md
@@ -110,7 +110,8 @@ a double dash to prevent input files being used as option arguments:
     --keep-classnames           Do not mangle/drop class names.
     --keep-fnames               Do not mangle/drop function names.  Useful for
                                 code relying on Function.prototype.name.
-    --module                    Input is an ES6 module
+    --module                    Input is an ES6 module. If `compress` or `mangle` is
+                                enabled then the `toplevel` option will be enabled.
     --name-cache <file>         File to hold mangled name mappings.
     --safari10                  Support non-standard Safari 10/11.
                                 Equivalent to setting `safari10: true` in `minify()`
@@ -498,7 +499,8 @@ if (result.error) throw result.error;
     Pass an object to specify custom [mangle property options](#mangle-properties-options).
 
 - `module` (default `false`) — Use when minifying an ES6 module. "use strict"
-  is implied and names can be mangled on the top scope.
+  is implied and names can be mangled on the top scope. If `compress` or
+  `mangle` is enabled then the `toplevel` option will be enabled.
 
 - `output` (default `null`) — pass an object if you wish to specify
   additional [output options](#output-options).  The defaults are optimized