diff --git a/src/nifreeze/model/base.py b/src/nifreeze/model/base.py
index 748285fef..eca1abeb6 100644
--- a/src/nifreeze/model/base.py
+++ b/src/nifreeze/model/base.py
@@ -96,7 +96,10 @@ def __init__(self, mask=None, **kwargs):
 
         # Setup brain mask
         if mask is None:
-            warn("No mask provided; consider using a mask to avoid issues in model optimization.")
+            warn(
+                "No mask provided; consider using a mask to avoid issues in model optimization.",
+                stacklevel=2,
+            )
 
         self._mask = mask
 
diff --git a/test/conftest.py b/test/conftest.py
index d66738c7e..f2bbbef0d 100644
--- a/test/conftest.py
+++ b/test/conftest.py
@@ -100,5 +100,6 @@ def pytest_terminal_summary(terminalreporter, exitstatus, config):
         terminalreporter.ensure_newline()
         terminalreporter.section("Werrors", sep="=", red=True, bold=True)
         terminalreporter.line(
-            f"Warnings as errors: Activated.\n{len(have_warnings)} warnings were raised and treated as errors.\n"
+            "Warnings as errors: Activated.\n"
+            f"{len(have_warnings)} warnings were raised and treated as errors.\n"
         )