diff --git a/pyproject.toml b/pyproject.toml
index 49783e6..c853e59 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -19,7 +19,7 @@ dependencies = [
     "sumo-wrapper-python>=1.0.3",
     "fmu-dataio",
     "openvds; sys_platform != 'darwin'",
-    "ert; sys_platform != 'windows'"
+    "ert; sys_platform != 'win32'"
 ]
 
 [project.optional-dependencies]