diff --git a/beat/core/test/test_format_extends.py b/beat/core/test/test_format_extends.py
index d71d5e26484beac867ce773b575b3b4962a058d1..cd7b9052c66c19e5822d7e73b2bb8899a7ef18b5 100644
--- a/beat/core/test/test_format_extends.py
+++ b/beat/core/test/test_format_extends.py
@@ -46,9 +46,9 @@ from . import prefix
 
 def test_invalid():
     df = DataFormat(prefix, "user/extended_unknown/1")  # not allowed
-    assert df.valid is False
-    assert df.errors[0].find("referred dataformat") != -1
-    assert df.errors[0].find("user/unknown/1") != -1
+    nose.tools.assert_false(df.valid)
+    nose.tools.assert_not_equal(df.errors[0].find("referred dataformat"), -1)
+    nose.tools.assert_not_equal(df.errors[0].find("user/unknown/1"), -1)
 
 
 # ----------------------------------------------------------
@@ -56,5 +56,7 @@ def test_invalid():
 
 def test_name_clash():
     df = DataFormat(prefix, "user/extended_name_clash/1")  # not allowed
-    assert df.valid is False
-    assert df.errors[0].find("clashes with an attribute with the same") != -1
+    nose.tools.assert_false(df.valid)
+    nose.tools.assert_not_equal(
+        df.errors[0].find("clashes with an attribute with the same"), -1
+    )