diff --git a/ultraplot/tests/conftest.py b/ultraplot/tests/conftest.py
index f296ab9d1..8564a9163 100644
--- a/ultraplot/tests/conftest.py
+++ b/ultraplot/tests/conftest.py
@@ -89,3 +89,11 @@ def pytest_configure(config):
             config.pluginmanager.register(StoreFailedMplPlugin(config))
     except Exception as e:
         print(f"Error during plugin configuration: {e}")
+    # Set a global default tolerance for mpl_image_compare unless overridden.
+    try:
+        if config.getoption("--mpl-default-tolerance") is None and not config.getini(
+            "mpl-default-tolerance"
+        ):
+            config.setini("mpl-default-tolerance", "3")
+    except Exception as e:
+        print(f"Error setting mpl default tolerance: {e}")