diff --git a/searx/webapp.py b/searx/webapp.py
index a6fabe9b1..b1b6f281d 100755
--- a/searx/webapp.py
+++ b/searx/webapp.py
@@ -1948,7 +1948,7 @@ class DFAFilter():
         self.delimit = '\x00'
 
     def add(self, keyword):
-        if not isinstance(keyword, unicode):
+        if not isinstance(keyword, str):
             keyword = keyword.decode('utf-8')
         keyword = keyword.lower()
         chars = keyword.strip()
@@ -1976,7 +1976,7 @@ class DFAFilter():
                 self.add(keyword.strip())
 
     def filter(self, message, repl="*"):
-        if not isinstance(message, unicode):
+        if not isinstance(message, str):
             message = message.decode('utf-8')
         message = message.lower()
         ret = []
diff --git a/searx/webapp1.py b/searx/webapp1.py
index 336d280fd..182ba80c4 100644
--- a/searx/webapp1.py
+++ b/searx/webapp1.py
@@ -2994,7 +2994,7 @@ class DFAFilter():
         self.delimit = '\x00'
 
     def add(self, keyword):
-        if not isinstance(keyword, unicode):
+        if not isinstance(keyword, str):
             keyword = keyword.decode('utf-8')
         keyword = keyword.lower()
         chars = keyword.strip()
@@ -3022,7 +3022,7 @@ class DFAFilter():
                 self.add(keyword.strip())
 
     def filter(self, message, repl="*"):
-        if not isinstance(message, unicode):
+        if not isinstance(message, str):
             message = message.decode('utf-8')
         message = message.lower()
         ret = []