diff --git a/lib/core/common.py b/lib/core/common.py
index fb7b168de..35f220256 100644
--- a/lib/core/common.py
+++ b/lib/core/common.py
@@ -2433,19 +2433,10 @@ def removeDynamicContent(page):
 def filterStringValue(value, regex, replace=None):
     """
     Returns string value consisting only of chars satisfying supplied
-    regular expression
+    regular expression (note: it has to be in form [...])
     """
 
-    retVal = ""
-
-    if value:
-        for char in value:
-            if re.search(regex, char):
-                retVal += char
-            elif replace:
-                retVal += replace
-
-    return retVal
+    return re.sub(regex.replace("[", "[^"), "", value or "")
 
 def filterControlChars(value):
     """
diff --git a/lib/techniques/union/use.py b/lib/techniques/union/use.py
index f9acda624..65964aa60 100644
--- a/lib/techniques/union/use.py
+++ b/lib/techniques/union/use.py
@@ -18,7 +18,6 @@ from lib.core.common import calculateDeltaSeconds
 from lib.core.common import clearConsoleLine
 from lib.core.common import dataToStdout
 from lib.core.common import extractRegexResult
-from lib.core.common import filterStringValue
 from lib.core.common import getConsoleWidth
 from lib.core.common import getUnicode
 from lib.core.common import initTechnique