diff --git a/pyproject.toml b/pyproject.toml
index 92a68e1fb..143fcf0de 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -43,6 +43,7 @@ dependencies = [
     "resfo-utilities>=0.1.1",
     "polars",
     "fastexcel",
+    "packaging>=26.3",
 ]
 [dependency-groups]
 dev = [
diff --git a/tests/conftest.py b/tests/conftest.py
index b6f3617cc..4a8479aef 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -2,15 +2,19 @@
 import os
 import shutil
 import subprocess
+from importlib.metadata import version
 from pathlib import Path
 
-import cwrap
 import pytest
 from hypothesis import HealthCheck, settings
+from packaging.version import Version
 from resdata import ResDataType
 from resdata.grid import GridGenerator
 from resdata.resfile import ResdataKW
 
+if Version(version("resdata")).major < 7:
+    import cwrap
+
 from tests import legacy_test_data
 
 # Timeout settings are unreliable both on CI and
@@ -121,7 +125,11 @@ def fixture_grid_prop():
     def wrapper(prop_name, value, grid_size, fname):
         prop = ResdataKW(prop_name, grid_size, ResDataType.RD_FLOAT)
         prop.assign(value)
-        with cwrap.open(fname, "w") as file:
-            prop.write_grdecl(file)
+        if Version(version("resdata")).major < 7:
+            with cwrap.open(fname, "w") as file:
+                prop.write_grdecl(file)
+        else:
+            with Path(fname).open(mode="w", encoding="utf-8") as file:
+                prop.write_grdecl(file)
 
     return wrapper
diff --git a/uv.lock b/uv.lock
index decc70ad2..4420c1b22 100644
--- a/uv.lock
+++ b/uv.lock
@@ -4,11 +4,11 @@ requires-python = ">=3.12"
 resolution-markers = [
     "python_full_version >= '3.15' and platform_machine == 'ARM64' and sys_platform == 'win32'",
     "python_full_version >= '3.15' and platform_machine != 'ARM64' and sys_platform == 'win32'",
+    "python_full_version >= '3.15' and sys_platform == 'emscripten'",
+    "python_full_version >= '3.15' and sys_platform != 'emscripten' and sys_platform != 'win32'",
     "python_full_version == '3.14.*' and platform_machine == 'ARM64' and sys_platform == 'win32'",
     "python_full_version == '3.14.*' and platform_machine != 'ARM64' and sys_platform == 'win32'",
-    "python_full_version >= '3.15' and sys_platform == 'emscripten'",
     "python_full_version == '3.14.*' and sys_platform == 'emscripten'",
-    "python_full_version >= '3.15' and sys_platform != 'emscripten' and sys_platform != 'win32'",
     "python_full_version == '3.14.*' and sys_platform != 'emscripten' and sys_platform != 'win32'",
     "python_full_version < '3.14' and platform_machine == 'ARM64' and sys_platform == 'win32'",
     "python_full_version < '3.14' and platform_machine != 'ARM64' and sys_platform == 'win32'",
@@ -3743,6 +3743,7 @@ dependencies = [
     { name = "fastexcel" },
     { name = "fmu-ensemble" },
     { name = "numpy" },
+    { name = "packaging" },
     { name = "pandas" },
     { name = "polars" },
     { name = "probabilit" },
@@ -3788,6 +3789,7 @@ requires-dist = [
     { name = "fastexcel" },
     { name = "fmu-ensemble", specifier = ">1.6.5" },
     { name = "numpy" },
+    { name = "packaging", specifier = ">=26.3" },
     { name = "pandas", specifier = ">=2" },
     { name = "polars" },
     { name = "probabilit", specifier = ">=0.4.1" },