diff --git a/README.md b/README.md
index 6375c60..48d4f06 100644
--- a/README.md
+++ b/README.md
@@ -132,7 +132,7 @@ This script born as a cross-platform alternative to `KindleComicParser` by **Dc5
 
 The app relies and includes the following scripts/binaries:
 
- - `DualMetaFix` script by Charles **K. Hendricks**. Released with GPL-3 License.
+ - `DualMetaFix` script by **K. Hendricks**. Released with GPL-3 License.
  - `rarfile.py` script &copy; 2005-2011 **Marko Kreen** <markokr@gmail.com>. Released with ISC License.
  - `image.py` class from **Alex Yatskov**'s [Mangle](https://github.com/FooSoft/mangle/) with subsequent [proDOOMman](https://github.com/proDOOMman/Mangle)'s and [Birua](https://github.com/Birua/Mangle)'s patches.
  - Icon is by **Nikolay Verin** ([http://ncrow.deviantart.com/](http://ncrow.deviantart.com/)) and released under [CC BY-NC-SA 3.0](http://creativecommons.org/licenses/by-nc-sa/3.0/) License.
diff --git a/kcc/KCC_gui.py b/kcc/KCC_gui.py
index 7cc66a4..c439f08 100644
--- a/kcc/KCC_gui.py
+++ b/kcc/KCC_gui.py
@@ -37,6 +37,7 @@ from PyQt5 import QtGui, QtCore, QtWidgets
 from xml.dom.minidom import parse
 from html.parser import HTMLParser
 from psutil import virtual_memory, Popen, Process
+from uuid import uuid4
 from .shared import md5Checksum
 from . import comic2ebook
 from . import dualmetafix
@@ -315,8 +316,8 @@ class DualMetaFixThread(QtCore.QRunnable):
         mobiPath = item.replace('.epub', '.mobi')
         move(mobiPath, mobiPath + '_toclean')
         try:
-            mobiedit = dualmetafix.DualMobiMetaFix(mobiPath + '_toclean')
-            open(mobiPath, 'wb').write(mobiedit.getresult())
+            # noinspection PyArgumentList
+            dualmetafix.DualMobiMetaFix(mobiPath + '_toclean', mobiPath, bytes(str(uuid4()), 'UTF-8'))
             self.signals.result.emit([True])
         except Exception as err:
             self.signals.result.emit([False, format(err)])
diff --git a/kcc/dualmetafix.py b/kcc/dualmetafix.py
index e99fb45..1c80b58 100644
--- a/kcc/dualmetafix.py
+++ b/kcc/dualmetafix.py
@@ -17,7 +17,8 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 import struct
-from uuid import uuid4
+import mmap
+import shutil
 
 
 class DualMetaFixException(Exception):
@@ -70,9 +71,7 @@ def replacesection(datain, secno, secdata):
     seclen = secend - secstart
     if len(secdata) != seclen:
         raise DualMetaFixException('section length change in replacesection')
-    datalst = [datain[0:secstart], secdata, datain[secend:]]
-    dataout = b''.join(datalst)
-    return dataout
+    datain[secstart:secstart+seclen] = secdata
 
 
 def get_exth_params(rec0):
@@ -135,12 +134,11 @@ def del_exth(rec0, exth_num):
 
 
 class DualMobiMetaFix:
-
-    def __init__(self, infile):
-        self.datain = open(infile, 'rb').read()
+    def __init__(self, infile, outfile, asin):
+        shutil.copyfile(infile, outfile)
+        f = open(outfile, "r+b")
+        self.datain = mmap.mmap(f.fileno(), 0)
         self.datain_rec0 = readsection(self.datain, 0)
-        # noinspection PyArgumentList
-        self.asin = bytes(str(uuid4()), 'UTF-8')
 
         # in the first mobi header
         # add 501 to "EBOK", add 113 as asin, add 504 as asin
@@ -149,9 +147,9 @@ class DualMobiMetaFix:
         rec0 = del_exth(rec0, 113)
         rec0 = del_exth(rec0, 504)
         rec0 = add_exth(rec0, 501, b'EBOK')
-        rec0 = add_exth(rec0, 113, self.asin)
-        rec0 = add_exth(rec0, 504, self.asin)
-        self.datain = replacesection(self.datain, 0, rec0)
+        rec0 = add_exth(rec0, 113, asin)
+        rec0 = add_exth(rec0, 504, asin)
+        replacesection(self.datain, 0, rec0)
 
         ver = getint(self.datain_rec0, mobi_version)
         self.combo = (ver != 8)
@@ -178,9 +176,9 @@ class DualMobiMetaFix:
         rec0 = del_exth(rec0, 113)
         rec0 = del_exth(rec0, 504)
         rec0 = add_exth(rec0, 501, b'EBOK')
-        rec0 = add_exth(rec0, 113, self.asin)
-        rec0 = add_exth(rec0, 504, self.asin)
-        self.datain = replacesection(self.datain, datain_kf8, rec0)
+        rec0 = add_exth(rec0, 113, asin)
+        rec0 = add_exth(rec0, 504, asin)
+        replacesection(self.datain, datain_kf8, rec0)
 
-    def getresult(self):
-        return self.datain
\ No newline at end of file
+        self.datain.flush()
+        self.datain.close()
\ No newline at end of file