diff --git a/repo2docker/app.py b/repo2docker/app.py
index 71171405..a2a9a92d 100755
--- a/repo2docker/app.py
+++ b/repo2docker/app.py
@@ -16,7 +16,6 @@ import shutil
 import sys
 import tempfile
 import time
-import warnings
 from urllib.parse import urlparse
 
 import entrypoints
@@ -267,7 +266,7 @@ class Repo2Docker(Application):
         """
         p = get_platform()
         if p == "linux/arm64":
-            warnings.warn(
+            self.log.warning(
                 "Building for linux/arm64 is experimental. "
                 "To use the recommended platform set --Repo2Docker.platform=linux/amd64. "
                 "To silence this warning set --Repo2Docker.platform=linux/arm64."
diff --git a/repo2docker/buildpacks/conda/__init__.py b/repo2docker/buildpacks/conda/__init__.py
index 2a3e694d..57f5d2ab 100644
--- a/repo2docker/buildpacks/conda/__init__.py
+++ b/repo2docker/buildpacks/conda/__init__.py
@@ -2,7 +2,6 @@
 
 import os
 import re
-import warnings
 from collections.abc import Mapping
 from functools import lru_cache
 
@@ -355,7 +354,7 @@ class CondaBuildPack(BaseImage):
     @property
     def py2(self):
         """Am I building a Python 2 kernel environment?"""
-        warnings.warn(
+        self.log.warning(
             "CondaBuildPack.py2 is deprecated in 2023.2. Use CondaBuildPack.separate_kernel_env.",
             DeprecationWarning,
             stacklevel=2,