diff --git a/definitions/grib2/template.4.horizontal.def b/definitions/grib2/template.4.horizontal.def
index 4702e0319..1ece521da 100644
--- a/definitions/grib2/template.4.horizontal.def
+++ b/definitions/grib2/template.4.horizontal.def
@@ -64,6 +64,11 @@ if (extraDim) {
     alias mars.levelist = dimension;
     alias mars.levtype = dimensionType;
 } else {
+    # ECC-1333: levtype should be read-only in GRIB2
+    concept mars.levtype(unknown,"marsLevtypeConcept.def",conceptsDir2,conceptsDir1):no_copy, read_only;
+    # GRIB-372: levelist alias does not pertain to surface parameters
+    transient tempLevtype = levtype; # Faster to copy the concept so we evaluate it once
+
     # See GRIB-74 why we store the pressureUnits in a transient
     transient tempPressureUnits=pressureUnits;
     # Same as typeOfLevel != "surface" but much quicker to evaluate
@@ -73,16 +78,11 @@ if (extraDim) {
             meta marsLevel scale(level,one,hundred) : read_only;
             alias mars.levelist=marsLevel;
         } else {
+            if (tempLevtype isnot "sfc" && tempLevtype isnot "o2d") {
             alias mars.levelist = level;
+            }
         }
     }
-    # ECC-1333: levtype should be read-only in GRIB2
-    concept mars.levtype(unknown,"marsLevtypeConcept.def",conceptsDir2,conceptsDir1):no_copy, read_only;
-    # GRIB-372: levelist alias does not pertain to surface parameters
-    transient tempLevtype = levtype; # Faster to copy the concept so we evaluate it once
-    if (tempLevtype is "sfc" || tempLevtype is "o2d") {
-        unalias mars.levelist;
-    }
 }
 
 # See ECC-854, ECC-1435, ECC-1451, ECC-1462