diff --git a/repo2docker/buildpacks/conda/__init__.py b/repo2docker/buildpacks/conda/__init__.py
index e7ec6bf5..aba09e47 100644
--- a/repo2docker/buildpacks/conda/__init__.py
+++ b/repo2docker/buildpacks/conda/__init__.py
@@ -31,6 +31,8 @@ class CondaBuildPack(BaseImage):
         ]
         if self.py2:
             env.append(('KERNEL_PYTHON_PREFIX', '${CONDA_DIR}/envs/kernel'))
+        else:
+            env.append(('KERNEL_PYTHON_PREFIX', '${NB_PYTHON_PREFIX}'))
         return env
 
     def get_path(self):