diff --git a/requirements.txt b/requirements.txt
index fee6791abd..879c5868d2 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -12,4 +12,4 @@ mda-xdrlib
 xarray
 cartopy
 pint
-netCDF4==1.7.0;sys_platform=="Windows"
+netCDF4==1.7.0;platform_system=="windows"