diff --git a/tests/test_circular.py b/tests/test_circular.py
index 07c66a3..d76d921 100644
--- a/tests/test_circular.py
+++ b/tests/test_circular.py
@@ -54,7 +54,15 @@ def test_max_recursion_depth(dumps):
     dumps(root)
 
     rl = sys.getrecursionlimit()
-    sys.setrecursionlimit(500)
+
+    if hasattr(sys, "pyston_version_info"):
+        # In Pyston setrecursionlimit() sets a lower bound on the number of frames,
+        # not an exact count. So set the limit lower:
+        sys.setrecursionlimit(100)
+    else:
+        # Otherwise set it to the exact value:
+        sys.setrecursionlimit(500)
+
     try:
         with pytest.raises(expected_exception):
             dumps(root)
diff --git a/tests/test_memory_leaks.py b/tests/test_memory_leaks.py
index 8d2116d..015ba73 100644
--- a/tests/test_memory_leaks.py
+++ b/tests/test_memory_leaks.py
@@ -9,11 +9,12 @@
 import io
 import datetime
 import gc
-import tracemalloc
 
 import pytest
 import rapidjson as rj
 
+tracemalloc = pytest.importorskip("tracemalloc")
+
 
 def object_hook(td):
     if '__td__' in td: