diff --git a/data/txt/sha256sums.txt b/data/txt/sha256sums.txt
index 09d55a182..f013144d1 100644
--- a/data/txt/sha256sums.txt
+++ b/data/txt/sha256sums.txt
@@ -163,7 +163,7 @@ fad6640f60eac8ad1b65895cbccc39154864843a2a0b0f2ac596d3227edcd4f6  lib/controller
 1947e6c69fbc2bdce91d2836e5c9c9535e397e9271ae4b4ef922f7a01857df5e  lib/controller/handler.py
 4608f21a4333c162ab3c266c903fda4793cc5834de30d06affe9b7566dd09811  lib/controller/__init__.py
 216c9399853b7454d36dcb552baf9f1169ec7942897ddc46504684325cb6ce00  lib/core/agent.py
-a61a74ba17331c419c03bc90d829ba74d183787f39fd902f50198202cb5b26c7  lib/core/bigarray.py
+440cbab6161f466158c63f0ee97873254655f670ca990fa26bdd0a6e54c42c2a  lib/core/bigarray.py
 8920eb3115ecd25933084af986f453362aa55a4bd15bfb9e75673239bd206acc  lib/core/common.py
 d53a8aecab8af8b8da4dc1c74d868f70a38770d34b1fa50cae4532cae7ce1c87  lib/core/compat.py
 ebe518089733722879f5a13e73020ebe55d46fb7410cacf292ca4ea1d9d1c56a  lib/core/convert.py
@@ -186,7 +186,7 @@ c4bfb493a03caf84dd362aec7c248097841de804b7413d0e1ecb8a90c8550bc0  lib/core/readl
 d1bd70c1a55858495c727fbec91e30af267459c8f64d50fabf9e4ee2c007e920  lib/core/replication.py
 1d0f80b0193ac5204527bfab4bde1a7aee0f693fd008e86b4b29f606d1ef94f3  lib/core/revision.py
 d2eb8e4b05ac93551272b3d4abfaf5b9f2d3ac92499a7704c16ed0b4f200db38  lib/core/session.py
-37d96cd99b3011c3173ac7ae3992fd3a8aa5caea892e9fd8ab5a1b442dee3aa0  lib/core/settings.py
+aa86123af7058e4d98ddaf50c40329c4ebf6b71233f605915ff3a21d34018449  lib/core/settings.py
 1c5eab9494eb969bc9ce118a2ea6954690c6851cbe54c18373c723b99734bf09  lib/core/shell.py
 4eea6dcf023e41e3c64b210cb5c2efc7ca893b727f5e49d9c924f076bb224053  lib/core/subprocessng.py
 cdd352e1331c6b535e780f6edea79465cb55af53aa2114dcea0e8bf382e56d1a  lib/core/target.py
diff --git a/lib/core/bigarray.py b/lib/core/bigarray.py
index 8a786d29a..5741b2e61 100644
--- a/lib/core/bigarray.py
+++ b/lib/core/bigarray.py
@@ -14,6 +14,7 @@ import itertools
 import os
 import sys
 import tempfile
+import threading
 import zlib
 
 from lib.core.compat import xrange
@@ -74,6 +75,7 @@ class BigArray(list):
         self.chunk_length = sys.maxsize
         self.cache = None
         self.filenames = set()
+        self._lock = threading.Lock()
         self._os_remove = os.remove
         self._size_counter = 0
 
@@ -95,18 +97,19 @@ class BigArray(list):
         return self
 
     def append(self, value):
-        self.chunks[-1].append(value)
+        with self._lock:
+            self.chunks[-1].append(value)
 
-        if self.chunk_length == sys.maxsize:
-            self._size_counter += _size_of(value)
-            if self._size_counter >= BIGARRAY_CHUNK_SIZE:
-                self.chunk_length = len(self.chunks[-1])
-                self._size_counter = None
+            if self.chunk_length == sys.maxsize:
+                self._size_counter += _size_of(value)
+                if self._size_counter >= BIGARRAY_CHUNK_SIZE:
+                    self.chunk_length = len(self.chunks[-1])
+                    self._size_counter = None
 
-        if len(self.chunks[-1]) >= self.chunk_length:
-            filename = self._dump(self.chunks[-1])
-            self.chunks[-1] = filename
-            self.chunks.append([])
+            if len(self.chunks[-1]) >= self.chunk_length:
+                filename = self._dump(self.chunks[-1])
+                self.chunks[-1] = filename
+                self.chunks.append([])
 
     def extend(self, value):
         for _ in value:
diff --git a/lib/core/settings.py b/lib/core/settings.py
index 22169d577..b3fcb83c7 100644
--- a/lib/core/settings.py
+++ b/lib/core/settings.py
@@ -19,7 +19,7 @@ from lib.core.enums import OS
 from thirdparty import six
 
 # sqlmap version (<major>.<minor>.<month>.<monthly commit>)
-VERSION = "1.9.5.19"
+VERSION = "1.9.5.20"
 TYPE = "dev" if VERSION.count('.') > 2 and VERSION.split('.')[-1] != '0' else "stable"
 TYPE_COLORS = {"dev": 33, "stable": 90, "pip": 34}
 VERSION_STRING = "sqlmap/%s#%s" % ('.'.join(VERSION.split('.')[:-1]) if VERSION.count('.') > 2 and VERSION.split('.')[-1] == '0' else VERSION, TYPE)