diff --git a/requirements/core.txt b/requirements/core.txt
index 7e55bd1fd5..fd50d69ce6 100644
--- a/requirements/core.txt
+++ b/requirements/core.txt
@@ -5,7 +5,7 @@
 
 cartopy
 #conda: proj4<5
-cf_units>=2
+cf-units>=2
 cftime==1.0.1
 dask[array]  #conda: dask
 matplotlib>=2,<3