diff --git a/lib/controller/checks.py b/lib/controller/checks.py
index 2476cd5ba..f3167a41f 100644
--- a/lib/controller/checks.py
+++ b/lib/controller/checks.py
@@ -66,13 +66,14 @@ from lib.core.settings import DEFAULT_GET_POST_DELIMITER
 from lib.core.settings import DUMMY_NON_SQLI_CHECK_APPENDIX
 from lib.core.settings import FORMAT_EXCEPTION_STRINGS
 from lib.core.settings import HEURISTIC_CHECK_ALPHABET
+from lib.core.settings import IDS_WAF_CHECK_PAYLOAD
+from lib.core.settings import IDS_WAF_CHECK_RATIO
+from lib.core.settings import IDS_WAF_CHECK_TIMEOUT
+from lib.core.settings import NON_SQLI_CHECK_PREFIX_SUFFIX_LENGTH
 from lib.core.settings import SUHOSIN_MAX_VALUE_LENGTH
 from lib.core.settings import SUPPORTED_DBMS
 from lib.core.settings import URI_HTTP_HEADER
 from lib.core.settings import UPPER_RATIO_BOUND
-from lib.core.settings import IDS_WAF_CHECK_PAYLOAD
-from lib.core.settings import IDS_WAF_CHECK_RATIO
-from lib.core.settings import IDS_WAF_CHECK_TIMEOUT
 from lib.core.threads import getCurrentThreadData
 from lib.request.connect import Connect as Request
 from lib.request.inject import checkBooleanExpression
@@ -932,7 +933,7 @@ def heuristicCheckSqlInjection(place, parameter):
 
     kb.heuristicMode = True
 
-    randStr1, randStr2 = randomStr(), randomStr()
+    randStr1, randStr2 = randomStr(NON_SQLI_CHECK_PREFIX_SUFFIX_LENGTH), randomStr(NON_SQLI_CHECK_PREFIX_SUFFIX_LENGTH)
     value = "%s%s%s" % (randStr1, DUMMY_NON_SQLI_CHECK_APPENDIX, randStr2)
     payload = "%s%s%s" % (prefix, "'%s" % value, suffix)
     payload = agent.payload(place, parameter, newValue=payload)
@@ -940,15 +941,17 @@ def heuristicCheckSqlInjection(place, parameter):
 
     paramType = conf.method if conf.method not in (None, HTTPMETHOD.GET, HTTPMETHOD.POST) else place
 
-    if value in (page or ""):
+    if value.lower() in (page or "").lower():
         infoMsg = "heuristic (XSS) test shows that %s parameter " % paramType
         infoMsg += "'%s' might be vulnerable to cross-site scripting attacks" % parameter
         logger.info(infoMsg)
 
-    if re.search(r"(?i)Failed opening[^\n]+%s" % randStr1, page or ""):
-        infoMsg = "heuristic (FI) test shows that %s parameter " % paramType
-        infoMsg += "'%s' might be vulnerable to file inclusion attacks" % parameter
-        logger.info(infoMsg)
+    for match in re.finditer("(?i)[^\n]*(no such file|failed (to )?open)[^\n]*", page or ""):
+        if randStr1.lower() in match.group(0).lower():
+            infoMsg = "heuristic (FI) test shows that %s parameter " % paramType
+            infoMsg += "'%s' might be vulnerable to file inclusion attacks" % parameter
+            logger.info(infoMsg)
+            break
 
     kb.heuristicMode = False
 
diff --git a/lib/core/settings.py b/lib/core/settings.py
index 52e2ba738..84a0c67e0 100644
--- a/lib/core/settings.py
+++ b/lib/core/settings.py
@@ -548,9 +548,12 @@ DNS_BOUNDARIES_ALPHABET = re.sub("[a-fA-F]", "", string.ascii_letters)
 # Alphabet used for heuristic checks
 HEURISTIC_CHECK_ALPHABET = ('"', '\'', ')', '(', ',', '.')
 
-# String used for dummy non-SQLi (e.g. XSS) check of a tested parameter value
+# String used for dummy non-SQLi (e.g. XSS) heuristic checks of a tested parameter value
 DUMMY_NON_SQLI_CHECK_APPENDIX = "<'\">"
 
+# Length of prefix and suffix used in non-SQLI heuristic checks
+NON_SQLI_CHECK_PREFIX_SUFFIX_LENGTH = 6
+
 # Connection chunk size (processing large responses in chunks to avoid MemoryError crashes - e.g. large table dump in full UNION injections)
 MAX_CONNECTION_CHUNK_SIZE = 10 * 1024 * 1024