diff --git a/config_utils.py b/config_utils.py
index 8f5a509..630eafc 100644
--- a/config_utils.py
+++ b/config_utils.py
@@ -1,7 +1,5 @@
 import json
-import logging
 import os
-import subprocess
 from collections.abc import Iterable
 
 import yaml
@@ -21,35 +19,9 @@ def read_yaml_config(file: str):
     return yaml.safe_load(open(file))
 
 
-def read_mk_config(file: str, design_dir: str | None = None):
-    logging.warning(
-        "Reading Makefile configuration files is an experimental feature and could be removed"
-    )
-    env_pre = {} if design_dir is None else {"DESIGN_HOME": design_dir}
-    mk_cg = "all:\n\t@env"
-    mk_tg = f"-include {file}\n{mk_cg}"
-    env_cg = subprocess.run(
-        "make -f -",
-        shell=True,
-        env=env_pre,
-        input=mk_cg,
-        capture_output=True,
-        text=True,
-    ).stdout.strip()
-    env_tg = subprocess.run(
-        "make -f -",
-        shell=True,
-        env=env_pre,
-        input=mk_tg,
-        capture_output=True,
-        text=True,
-    ).stdout.strip()
-    env_diff = set(env_tg.split("\n")) - set(env_cg.split("\n"))
-    config = dict(i.split("=", 1) for i in env_diff)
-    return config
-
-
-def read_config(basename: str, formats: Iterable[str], design_dir: str | None = None):
+def read_config(
+    basename: str, formats: Iterable[str] = ("json",), design_dir: str | None = None
+):
     for fmt in formats:
         file = f"{basename}.{fmt}"
         if os.path.exists(file):
@@ -57,8 +29,6 @@ def read_config(basename: str, formats: Iterable[str], design_dir: str | None =
                 return read_json_config(file)
             elif fmt == "yaml":
                 return read_yaml_config(file)
-            elif fmt == "mk":
-                return read_mk_config(file)
             else:
                 raise ConfigFileError(f"Unexpected configuration file format: {fmt}")
     raise ConfigFileError(
@@ -86,14 +56,12 @@ def write_mk_config(config: dict, file: str):
             print(f"export {key} = {value}", file=f)
 
 
-def write_config(config: dict, basename: str, formats: Iterable[str]):
+def write_config(config: dict, basename: str, formats: Iterable[str] = ("json",)):
     for fmt in formats:
         file = f"{basename}.{fmt}"
         if fmt == "json":
             write_json_config(config, file)
         elif fmt == "yaml":
             write_yaml_config(config, file)
-        elif fmt == "mk":
-            write_mk_config(config, file)
         else:
             raise ConfigFileError("Unexpected configuration file format: {fmt}")
diff --git a/project.py b/project.py
index 4cd5450..b6f4a22 100644
--- a/project.py
+++ b/project.py
@@ -500,10 +500,10 @@ class Project:
         tt_version = self.get_tt_tools_version()
         workflow_url = self.get_workflow_url()
 
-        config = read_config("src/config", ("json", "tcl"))
-        user_config = read_config("src/user_config", ("json",))
+        config = read_config("src/config")
+        user_config = read_config("src/user_config")
         config.update(user_config)
-        write_config(config, "src/config_merged", ("json",))
+        write_config(config, "src/config_merged")
 
         shutil.rmtree("runs/wokwi", ignore_errors=True)
         os.makedirs("runs/wokwi", exist_ok=True)