diff --git a/tests/conftest.py b/tests/conftest.py
index 8389f8c8..35768f59 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -6,6 +6,7 @@
 # LICENSE file in the root directory of this source tree)
 #######################################################################
 import os
+import sys
 
 import pytest
 
@@ -14,6 +15,15 @@
 
 def pytest_configure(config):
     blosc2.print_versions()
+    if sys.platform != "emscripten":
+        # Using the defaults for nthreads can be very time consuming for tests.
+        # Fastest runtime (95 sec) for the whole test suite (Mac Mini M4 Pro)
+        # blosc2.set_nthreads(1)
+        # Second best runtime (101 sec), but still contained, and
+        # actually tests multithreading.
+        blosc2.set_nthreads(2)
+        # This makes the worst time (242 sec)
+        # blosc2.set_nthreads(blosc2.nthreads)  # worst runtime ()
 
 
 @pytest.fixture(scope="session")