diff --git a/hexgen/util.py b/hexgen/util.py
index 17fe25c..bacdb92 100644
--- a/hexgen/util.py
+++ b/hexgen/util.py
@@ -164,11 +164,11 @@ def __enter__(self):
         if self.debug:
             print(self.text.ljust(50), end="")
             print('starting...')
-        self.start = time.clock()
+        self.start = time.perf_counter()
         return self
 
     def __exit__(self, *args):
-        self.end = time.clock()
+        self.end = time.perf_counter()
         self.interval = self.end - self.start
         if self.debug:
             print(self.text.ljust(50), end="")