diff --git a/LICENSE b/LICENSE
index 6c21aa7..2ef16f2 100644
--- a/LICENSE
+++ b/LICENSE
@@ -1,9 +1,9 @@
 MIT License
 
-Copyright (c) 2017-2022 Marc Robledo
+Copyright (c) 2017-2023 Marc Robledo
 
 This project incorporates components from Octicons
-(https://github.com/primer/octicons/) Copyright (c) 2022 GitHub Inc.,
+(https://github.com/primer/octicons/) Copyright (c) 2023 GitHub Inc.,
 also released under MIT license.
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
diff --git a/_cache_service_worker.js b/_cache_service_worker.js
index bc3ddc4..cf9e35c 100644
--- a/_cache_service_worker.js
+++ b/_cache_service_worker.js
@@ -14,7 +14,7 @@
 */
 
 var PRECACHE_ID='rom-patcher-js';
-var PRECACHE_VERSION='v27';
+var PRECACHE_VERSION='v27b';
 var PRECACHE_URLS=[
 	'/RomPatcher.js/','/RomPatcher.js/index.html',
 	'/RomPatcher.js/manifest.json',
diff --git a/index.html b/index.html
index dfc4ab9..a342ebe 100644
--- a/index.html
+++ b/index.html
@@ -179,7 +179,7 @@
 		<button id="button-settings" class="button-outer"><img src="style/icon_settings.svg" class="icon settings" /> <span data-localize="settings">Settings</span></button>
 	</div>
 
-	Rom Patcher JS <small>v2.7</small> by <a href="/">Marc Robledo</a>
+	Rom Patcher JS <small>v2.7.1</small> by <a href="/">Marc Robledo</a>
 	<br />
 	<img src="style/icon_github.svg" class="icon github" /> <a href="https://github.com/marcrobledo/RomPatcher.js/" target="_blank">See on GitHub</a>
 	<img src="style/icon_heart.svg" class="icon heart" /> <a href="https://www.paypal.me/marcrobledo/5" target="_blank" rel="nofollow">Donate</a>
diff --git a/js/MarcFile.js b/js/MarcFile.js
index f2e4e9a..ec86c08 100644
--- a/js/MarcFile.js
+++ b/js/MarcFile.js
@@ -1,4 +1,4 @@
-/* MODDED VERSION OF MarcFile.js v20181020 - Marc Robledo 2014-2018 - http://www.marcrobledo.com/license */
+/* MODDED VERSION OF MarcFile.js v20230202 - Marc Robledo 2014-2023 - http://www.marcrobledo.com/license */
 
 function MarcFile(source, onLoad){	
 	if(typeof source==='object' && source.files) /* get first file only if source is input with multiple files */
@@ -146,6 +146,13 @@ MarcFile.prototype.save=function(){
 }
 
 
+MarcFile.prototype.getExtension=function(){
+	var ext=this.fileName? this.fileName.toLowerCase().match(/\.(\w+)$/) : '';
+
+	return ext? ext[1] : '';
+}
+
+
 MarcFile.prototype.readU8=function(){
 	this._lastRead=this._u8array[this.offset];
 
diff --git a/js/RomPatcher.js b/js/RomPatcher.js
index 2d5fbf5..de5070c 100644
--- a/js/RomPatcher.js
+++ b/js/RomPatcher.js
@@ -1,4 +1,4 @@
-/* Rom Patcher JS v20221110 - Marc Robledo 2016-2022 - http://www.marcrobledo.com/license */
+/* Rom Patcher JS v20230202 - Marc Robledo 2016-2023 - http://www.marcrobledo.com/license */
 
 const TOO_BIG_ROM_SIZE=67108863;
 const HEADERS_INFO=[
@@ -141,7 +141,7 @@ function fetchPatch(customPatchIndex, compressedFileIndex){
 				patchFile=CUSTOM_PATCHER[customPatchIndex].fetchedFile=new MarcFile(arrayBuffer);
 				patchFile.fileName=customPatch.file.replace(/^.*[\/\\]/g,'');
 
-				if(patchFile.readString(4).startsWith(ZIP_MAGIC))
+				if(patchFile.getExtension()==='zip' && patchFile.readString(4).startsWith(ZIP_MAGIC))
 					ZIPManager.parseFile(CUSTOM_PATCHER[customPatchIndex].fetchedFile, compressedFileIndex);
 				else
 					parseCustomPatch(CUSTOM_PATCHER[customPatchIndex]);
@@ -161,7 +161,7 @@ function fetchPatch(customPatchIndex, compressedFileIndex){
 				patchFile=CUSTOM_PATCHER[customPatchIndex].fetchedFile=new MarcFile(xhr.response);
 				patchFile.fileName=customPatch.file.replace(/^.*[\/\\]/g,'');
 
-				if(patchFile.readString(4).startsWith(ZIP_MAGIC))
+				if(patchFile.getExtension()==='zip' && patchFile.readString(4).startsWith(ZIP_MAGIC))
 					ZIPManager.parseFile(CUSTOM_PATCHER[customPatchIndex].fetchedFile, compressedFileIndex);
 				else
 					parseCustomPatch(CUSTOM_PATCHER[customPatchIndex]);
@@ -184,7 +184,7 @@ function _parseROM(){
 	el('checkbox-addheader').checked=false;
 	el('checkbox-removeheader').checked=false;
 
-	if(romFile.readString(4).startsWith(ZIP_MAGIC)){
+	if(romFile.getExtension()==='zip' && romFile.readString(4).startsWith(ZIP_MAGIC)){
 		ZIPManager.parseFile(romFile);
 		setTabApplyEnabled(false);
 	}else{
@@ -653,7 +653,7 @@ function _readPatchFile(){
 	patchFile.littleEndian=false;
 
 	var header=patchFile.readString(6);
-	if(header.startsWith(ZIP_MAGIC)){
+	if(patchFile.getExtension()==='zip' && header.startsWith(ZIP_MAGIC)){
 		patch=false;
 		validateSource();
 		setTabApplyEnabled(false);