diff --git a/lib/core/option.py b/lib/core/option.py
index 8282f5ca7..17a6d76a9 100644
--- a/lib/core/option.py
+++ b/lib/core/option.py
@@ -1463,6 +1463,7 @@ def __setKnowledgeBaseAttributes(flushAll=True):
     kb.matchRatio = None
     kb.mergeCookies = None
     kb.multiThreadMode = False
+    kb.negativeLogic = False
     kb.nullConnection = None
     kb.pageTemplate = None
     kb.pageTemplates = dict()
diff --git a/lib/request/comparison.py b/lib/request/comparison.py
index 44c76d114..e0329bea0 100644
--- a/lib/request/comparison.py
+++ b/lib/request/comparison.py
@@ -35,21 +35,24 @@ def comparison(page, headers, code=None, getRatioValue=False, pageLength=None):
     seqMatcher = getCurrentThreadData().seqMatcher
     seqMatcher.set_seq1(kb.pageTemplate)
 
+    def _(condition):
+        #condition = not condition if kb.negativeLogic else condition
+        return condition if not getRatioValue else (MAX_RATIO if condition else MIN_RATIO)
+
     if any([conf.string, conf.regexp]):
         rawResponse = "%s%s" % (listToStrValue(headers.headers if headers else ""), page)
 
         # String to match in page when the query is valid
         if conf.string:
-            condition = conf.string in rawResponse
-            return condition if not getRatioValue else (MAX_RATIO if condition else MIN_RATIO)
+            return _(conf.string in rawResponse)
 
         # Regular expression to match in page when the query is valid
         if conf.regexp:
-            condition = re.search(conf.regexp, rawResponse, re.I | re.M) is not None
-            return condition if not getRatioValue else (MAX_RATIO if condition else MIN_RATIO)
+            return _(re.search(conf.regexp, rawResponse, re.I | re.M) is not None)
 
+    # HTTP code to match when the query is valid
     if isinstance(code, int) and conf.code:
-        return code == conf.code
+        return _(conf.code == code)
 
     if page:
         # In case of an DBMS error page return None
diff --git a/lib/request/inject.py b/lib/request/inject.py
index c376866d8..83f8bf9e1 100644
--- a/lib/request/inject.py
+++ b/lib/request/inject.py
@@ -414,6 +414,9 @@ def getValue(expression, blind=True, inband=True, error=True, time=True, fromUse
             if blind and isTechniqueAvailable(PAYLOAD.TECHNIQUE.BOOLEAN) and not found:
                 kb.technique = PAYLOAD.TECHNIQUE.BOOLEAN
 
+                pushValue(kb.negativeLogic)
+                kb.negativeLogic = "OR NOT" in kb.injection.data[kb.technique].vector
+
                 if expected == EXPECTED.BOOL:
                     value = __goBooleanProxy(booleanExpression)
                 else:
@@ -422,6 +425,8 @@ def getValue(expression, blind=True, inband=True, error=True, time=True, fromUse
                 count += 1
                 found = (value is not None) or (value is None and expectingNone) or count >= MAX_TECHNIQUES_PER_VALUE
 
+                kb.negativeLogic = popValue()
+
             if time and (isTechniqueAvailable(PAYLOAD.TECHNIQUE.TIME) or isTechniqueAvailable(PAYLOAD.TECHNIQUE.STACKED)) and not found:
                 if isTechniqueAvailable(PAYLOAD.TECHNIQUE.TIME):
                     kb.technique = PAYLOAD.TECHNIQUE.TIME