diff --git a/etc/environment.yml b/etc/environment.yml
index 620214b14..a3228f805 100644
--- a/etc/environment.yml
+++ b/etc/environment.yml
@@ -14,7 +14,7 @@ dependencies:
   # codegen
   - boltons>=1.0
   - Jinja2>=3.0
-  - modflow-devtools>=1.7.0
+  - modflow-devtools>=1.7.0,!=1.9.0,<2
   - tomli
   - tomli-w
 
diff --git a/pyproject.toml b/pyproject.toml
index 1ad5ce709..a98ca7407 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -37,7 +37,7 @@ dev = ["flopy[codegen,lint,test,optional,doc]", "tach"]
 codegen = [
     "Jinja2>=3.0",
     "boltons",
-    "modflow-devtools>=1.7.0",
+    "modflow-devtools>=1.7.0,!=1.9.0,<2",
     "tomli",
     "tomli-w"
 ]
@@ -51,7 +51,7 @@ test = [
     "jupyter",
     "jupyter_client >=8.4.0", # avoid datetime.utcnow() deprecation warning
     "jupytext",
-    "modflow-devtools>=1.7.0",
+    "modflow-devtools>=1.7.0,!=1.9.0,<2",
     "pytest !=8.1.0",
     "pytest-benchmark",
     "pytest-cov",