fix

src/Module.js

@@ -539,14 +539,16 @@ export default class Module {
 					const { start, end } = reference;
 					const name = declaration.render( es6 );
 
-					if ( reference.name !== name ) {
+					// the second part of this check is necessary because of
+					// namespace optimisation – name of `foo.bar` could be `bar`
+					if ( reference.name === name && name.length === reference.end - reference.start ) return;
+
 					if ( reference.isShorthandProperty ) {
 						magicString.insert( end, `: ${name}` );
 					} else {
 						magicString.overwrite( start, end, name, true );
 					}
 				}
-				}
 			});
 
 			// modify exports as necessary