diff --git a/benchmarks/asv_delegated_conda.py b/benchmarks/asv_delegated_conda.py
index 34312bad..30810309 100644
--- a/benchmarks/asv_delegated_conda.py
+++ b/benchmarks/asv_delegated_conda.py
@@ -114,6 +114,7 @@ def _prep_env(self) -> None:
         message = f"Running delegated environment management for: {self.name}"
         log.info(message)
         env_path = Path(self._path)
+        environ["ESMFMKFILE"] = str(env_path / "lib" / "esmf.mk")
 
         def copy_asv_files(src_parent: Path, dst_parent: Path) -> None:
             """For copying between self._path and a temporary cache."""
diff --git a/benchmarks/benchmarks/generate_data.py b/benchmarks/benchmarks/generate_data.py
index 34c7ab5c..dc9127b0 100644
--- a/benchmarks/benchmarks/generate_data.py
+++ b/benchmarks/benchmarks/generate_data.py
@@ -16,6 +16,7 @@
 from pathlib import Path
 import re
 from subprocess import CalledProcessError, check_output, run
+import sys
 from textwrap import dedent
 from warnings import warn
 
@@ -55,6 +56,8 @@
 #  False forces a benchmark run to re-make all the data files.
 REUSE_DATA = True
 
+ESMFMKFILE = "ESMFMKFILE"
+
 
 def run_function_elsewhere(func_to_run, *args, **kwargs):
     """
@@ -90,9 +93,12 @@ def run_function_elsewhere(func_to_run, *args, **kwargs):
         f"{func_to_run.__name__}(" + ",".join(func_call_term_strings) + ")"
     )
     python_string = "\n".join([func_string, func_call_string])
+    old_esmf_mk_file = environ.get(ESMFMKFILE, None)
+    environ[ESMFMKFILE] = str(Path(sys.executable).parents[1] / "lib" / "esmf.mk")
     result = run(
         [DATA_GEN_PYTHON, "-c", python_string], capture_output=True, check=True
     )
+    environ[ESMFMKFILE] = old_esmf_mk_file
     return result.stdout
 
 
diff --git a/noxfile.py b/noxfile.py
index 46f55de7..58b1436b 100644
--- a/noxfile.py
+++ b/noxfile.py
@@ -392,8 +392,6 @@ def benchmarks(
             Path(".nox").rglob(f"tests*/bin/python{PY_VER}")
         ).resolve()
         session.env[data_gen_var] = data_gen_python
-    esmf_mk_file = data_gen_python.parents[1] / "lib" / "esmf.mk"
-    session.env[ESMFMKFILE] = esmf_mk_file
 
     print("Running ASV...")
     session.cd("benchmarks")