diff --git a/definitions/grib2/template.4.chemical.def b/definitions/grib2/template.4.chemical.def
index 45080ddf9..a1e3b32e2 100644
--- a/definitions/grib2/template.4.chemical.def
+++ b/definitions/grib2/template.4.chemical.def
@@ -1,6 +1,7 @@
 # (C) Copyright 2005- ECMWF.
 
-constant paramType = "chemical" ;
+transient paramType="chemical";
+unalias mars.paramtype ;
 alias mars.paramtype = paramType ;
 
 # Atmospheric chemical or physical constituent type
diff --git a/definitions/grib2/template.4.parameter.def b/definitions/grib2/template.4.parameter.def
index 84d7f3cbf..2b6da0061 100644
--- a/definitions/grib2/template.4.parameter.def
+++ b/definitions/grib2/template.4.parameter.def
@@ -1,5 +1,8 @@
 # (C) Copyright 2005- ECMWF.
 
+transient paramType = "base";
+alias mars.paramtype = paramType ;
+
 # Parameter category
 codetable[1] parameterCategory ('4.1.[discipline:l].table',masterDir,localDir) : dump;