diff --git a/lib/core/option.py b/lib/core/option.py
index fa98d58a1..7a12a96f8 100644
--- a/lib/core/option.py
+++ b/lib/core/option.py
@@ -957,6 +957,7 @@ def __setConfAttributes():
     conf.scheme          = None
     #conf.seqMatcher      = difflib.SequenceMatcher(lambda x: x in " \t")
     conf.seqMatcher      = difflib.SequenceMatcher(None)
+    conf.seqLock         = None
     conf.sessionFP       = None
     conf.start           = True
     conf.threadException = False
diff --git a/lib/request/comparison.py b/lib/request/comparison.py
index 229b6a4e0..6e15ee594 100644
--- a/lib/request/comparison.py
+++ b/lib/request/comparison.py
@@ -65,9 +65,15 @@ def comparison(page, headers=None, getSeqMatcher=False):
         else:
             return False
 
+    if conf.seqLock:
+        conf.seqLock.acquire()
+
     conf.seqMatcher.set_seq2(page)
     ratio = round(conf.seqMatcher.ratio(), 3)
 
+    if conf.seqLock:
+        conf.seqLock.release()
+
     # If the url is stable and we did not set yet the match ratio and the
     # current injected value changes the url page content
     if conf.matchRatio is None:
diff --git a/lib/techniques/blind/inference.py b/lib/techniques/blind/inference.py
index 6626b9d92..50c502d8d 100644
--- a/lib/techniques/blind/inference.py
+++ b/lib/techniques/blind/inference.py
@@ -153,6 +153,7 @@ def bisection(payload, expression, length=None, charsetType=None, firstChar=None
         index   = [ firstChar ]    # As list for python nested function scoping
         idxlock = threading.Lock()
         iolock  = threading.Lock()
+        conf.seqLock = threading.Lock()
 
         def downloadThread():
             try:
@@ -237,6 +238,7 @@ def bisection(payload, expression, length=None, charsetType=None, firstChar=None
         if conf.verbose >= 1 and not showEta and infoMsg:
             dataToStdout(infoMsg)
 
+        conf.seqLock = None
     else:
         index = firstChar