diff --git a/tornado/test/runtests.py b/tornado/test/runtests.py
index d5bd769..e4f938d 100644
--- a/tornado/test/runtests.py
+++ b/tornado/test/runtests.py
@@ -137,6 +137,8 @@ def main():
     # 2.7 and 3.2
     warnings.filterwarnings("ignore", category=DeprecationWarning,
                             message="Please use assert.* instead")
+    warnings.filterwarnings("ignore", category=PendingDeprecationWarning,
+                            message="Please use assert.* instead")
     # Twisted 15.0.0 triggers some warnings on py3 with -bb.
     warnings.filterwarnings("ignore", category=BytesWarning,
                             module=r"twisted\..*")