diff --git a/sphere/instruments/keywords_irdifs.dat b/sphere/instruments/keywords_irdifs.dat
index 0e4be77..7566418 100644
--- a/sphere/instruments/keywords_irdifs.dat
+++ b/sphere/instruments/keywords_irdifs.dat
@@ -60,11 +60,16 @@ HIERARCH ESO AOS HOLOOP STATE
 HIERARCH ESO AOS IRLOOP STATE
 HIERARCH ESO AOS PUPLOOP STATE
 
-# CPI
+# CPI - derotator
 HIERARCH ESO INS4 DROT2 BEGIN
 HIERARCH ESO INS4 DROT2 END
 HIERARCH ESO INS4 DROT2 POSANG
 
+# CPI - half-wave plate
+HIERARCH ESO INS4 DROT3 BEGIN
+HIERARCH ESO INS4 DROT3 END
+HIERARCH ESO INS4 DROT3 POSANG
+
 # IRDIS
 HIERARCH ESO INS1 PAC X
 HIERARCH ESO INS1 PAC Y