diff --git a/.github/workflows/contrib_rerun_py.yml b/.github/workflows/contrib_rerun_py.yml
index 38e0ed4d135b..c81c2b12f5c2 100644
--- a/.github/workflows/contrib_rerun_py.yml
+++ b/.github/workflows/contrib_rerun_py.yml
@@ -93,7 +93,7 @@ jobs:
 
       - name: Run unit tests
         shell: bash
-        run: cd rerun_py/tests && pytest
+        run: cd rerun_py/tests && pytest -c ../pyproject.toml
 
       - name: Run e2e test
         shell: bash
diff --git a/.github/workflows/reusable_build_and_test_wheels.yml b/.github/workflows/reusable_build_and_test_wheels.yml
index 2ddae31ac99e..1d45dcd4b6b3 100644
--- a/.github/workflows/reusable_build_and_test_wheels.yml
+++ b/.github/workflows/reusable_build_and_test_wheels.yml
@@ -245,7 +245,7 @@ jobs:
       - name: Run unit tests
         if: needs.set-config.outputs.RUN_TESTS == 'true'
         shell: bash
-        run: cd rerun_py/tests && pytest
+        run: cd rerun_py/tests && pytest -c ../pyproject.toml
 
       - name: Run e2e test
         if: needs.set-config.outputs.RUN_TESTS == 'true'
diff --git a/justfile b/justfile
index b4d519a7cae4..d011861c70f0 100644
--- a/justfile
+++ b/justfile
@@ -113,7 +113,7 @@ py-lint:
 
 # Run fast unittests
 py-test:
-    python -m pytest -vv rerun_py/tests/unit/
+    python -m pytest -vv -c rerun_py/pyproject.toml rerun_py/tests/unit/
 
 # Run tests on all supported Python versions (through nox)
 py-test-allpy:
diff --git a/rerun_py/pyproject.toml b/rerun_py/pyproject.toml
index 31149866e904..777826f99280 100644
--- a/rerun_py/pyproject.toml
+++ b/rerun_py/pyproject.toml
@@ -119,3 +119,10 @@ include = ["rerun_sdk.pth", "rerun_sdk/rerun_demo/colmap_fiat.rrd"]
 locked = true
 name = "rerun_bindings"                                             # name of the .so library that the Python module will import
 python-packages = ["rerun_sdk/rerun", "rerun_sdk/rerun_demo"]
+
+[tool.pytest.ini_options]
+# These conform to Python's Warning Filter syntax:
+# https://docs.python.org/3/library/warnings.html#warning-filter
+filterwarnings = """
+error
+"""
diff --git a/rerun_py/rerun_sdk/rerun/_image.py b/rerun_py/rerun_sdk/rerun/_image.py
index 3bc106c0db4d..226d8589c569 100644
--- a/rerun_py/rerun_sdk/rerun/_image.py
+++ b/rerun_py/rerun_sdk/rerun/_image.py
@@ -102,9 +102,9 @@ def __init__(
         if (path is None) == (contents is None):
             raise ValueError("Must provide exactly one of 'path' or 'contents'")
 
-        buffer: IO[bytes] | None = None
+        buffer: IO[bytes] | None
         if path is not None:
-            buffer = open(path, "rb")
+            buffer = io.BytesIO(pathlib.Path(path).read_bytes())
         elif isinstance(contents, bytes):
             buffer = io.BytesIO(contents)
         else:
diff --git a/rerun_py/rerun_sdk/rerun/archetypes/asset3d_ext.py b/rerun_py/rerun_sdk/rerun/archetypes/asset3d_ext.py
index 31981d1d3fa0..e9477fa03e4f 100644
--- a/rerun_py/rerun_sdk/rerun/archetypes/asset3d_ext.py
+++ b/rerun_py/rerun_sdk/rerun/archetypes/asset3d_ext.py
@@ -74,7 +74,7 @@ def __init__(
             if path is None:
                 blob = contents
             else:
-                blob = open(path, "rb").read()
+                blob = pathlib.Path(path).read_bytes()
                 if media_type is None:
                     media_type = guess_media_type(str(path))