diff --git a/repo2docker/buildpacks/conda/__init__.py b/repo2docker/buildpacks/conda/__init__.py
index 7b92a138..817e8370 100644
--- a/repo2docker/buildpacks/conda/__init__.py
+++ b/repo2docker/buildpacks/conda/__init__.py
@@ -154,7 +154,7 @@ class CondaBuildPack(BaseImage):
             "conda/activate-conda.sh": "/etc/profile.d/activate-conda.sh",
         }
         py_version = self.python_version
-        self.log.info("Building conda environment for python={py_version}\n")
+        self.log.info(f"Building conda environment for python={py_version}\n")
         # Select the frozen base environment based on Python version.
         # avoids expensive and possibly conflicting upgrades when changing
         # major Python versions during upgrade.