diff --git a/definitions/grib2/local/ecmf/section4_extras.def b/definitions/grib2/local/ecmf/section4_extras.def
index 2477b2481..0d70c1ac9 100644
--- a/definitions/grib2/local/ecmf/section4_extras.def
+++ b/definitions/grib2/local/ecmf/section4_extras.def
@@ -4,7 +4,7 @@
 if (centre is "ecmf" or datasetForLocal is "era6") {
  concept modelName(unknown, "modelNameConcept.def", conceptsMasterDir, conceptsLocalDirAll): no_copy, dump, read_only;
 
- if (!(modelName is "unknown")) {
+ if (modelName isnot "unknown") {
     concept modelVersion(unknown, "modelVersionConcept_[modelName].def", conceptsMasterDir, conceptsLocalDirAll): no_copy, dump, read_only;
     # alias ls.model = modelName;
     # alias mars.model = modelName;
diff --git a/definitions/grib2/post_meta_data.hook.products_12.def b/definitions/grib2/post_meta_data.hook.products_12.def
index f01e08f71..e80da9e03 100644
--- a/definitions/grib2/post_meta_data.hook.products_12.def
+++ b/definitions/grib2/post_meta_data.hook.products_12.def
@@ -9,6 +9,6 @@ concept destineOrigin(unknown, "destineOriginConcept.def", conceptsDir2, concept
 unalias mars.domain;
 
 # ECC-1796: stepRange indexing for DestinE ExtremesDT and On-Demand ExtremesDT data
-if ( defined(dataset) && !(dataset is "climate-dt") ) {
+if ( defined(dataset) && dataset isnot "climate-dt" ) {
     alias mars.step=stepRange;
 }
diff --git a/definitions/grib2/section.4.def b/definitions/grib2/section.4.def
index c40709877..edb34d9b7 100644
--- a/definitions/grib2/section.4.def
+++ b/definitions/grib2/section.4.def
@@ -51,7 +51,7 @@ concept datasetForLocal(unknown) {
   "unknown" = { dummy=1; }
 }
 
-if (!(datasetForLocal is "unknown")) {
+if (datasetForLocal isnot "unknown") {
    constant conceptsDir2 = "grib2/localConcepts/[datasetForLocal]": hidden;
    constant conceptsDir1 = "grib2": hidden;
 }
diff --git a/definitions/mars/grib.mmsf.an.def b/definitions/mars/grib.mmsf.an.def
index 0a489319c..86ccb55b5 100644
--- a/definitions/mars/grib.mmsf.an.def
+++ b/definitions/mars/grib.mmsf.an.def
@@ -1,15 +1,16 @@
 #no step in type an
 unalias mars.step;
 
-if (class is "od") { alias mars.system = systemNumber; }
-if (class is "me") { alias mars.system = systemNumber; }
-if (class is "en") { alias mars.system = systemNumber; }
-if (class is "c3") { alias mars.system = systemNumber; }
-if (class is "ci") { alias mars.system = systemNumber; }
+if (class is "od" || class is "me" || class is "en" ||
+    class is "c3" || class is "ci")
+{
+   alias mars.system = systemNumber;
+}
+
 alias mars.number = perturbationNumber;
 alias mars.method = methodNumber;
 
-if (!(class is "gw")) { # ECC-1448
+if (class isnot "gw") { # ECC-1448
     alias mars.origin = centre;
 }
 
@@ -20,4 +21,3 @@ if (centre == 80 && subCentre == 98 && class is "c3") {
 }
 
 if (class is "ci") { unalias mars.method; }
-
diff --git a/definitions/mars/grib.mmsf.fc.def b/definitions/mars/grib.mmsf.fc.def
index c002f9d76..30b2f7394 100644
--- a/definitions/mars/grib.mmsf.fc.def
+++ b/definitions/mars/grib.mmsf.fc.def
@@ -4,15 +4,16 @@ if (levtype is "o2d" || levtype is "o3d") {
    alias mars.step = endStep;
 }
 
-if (class is "od") { alias mars.system = systemNumber; }
-if (class is "me") { alias mars.system = systemNumber; }
-if (class is "en") { alias mars.system = systemNumber; }
-if (class is "c3") { alias mars.system = systemNumber; }
-if (class is "ci") { alias mars.system = systemNumber; }
+if (class is "od" || class is "me" || class is "en" ||
+    class is "c3" || class is "ci")
+{
+   alias mars.system = systemNumber;
+}
+
 alias mars.number = perturbationNumber;
 alias mars.method = methodNumber;
 
-if (!(class is "gw")) { # ECC-1448
+if (class isnot "gw") { # ECC-1448
     alias mars.origin = centre;
 }
 
@@ -23,4 +24,3 @@ if (centre == 80 && subCentre == 98 && class is "c3") {
 }
 
 if (class is "ci") { unalias mars.method; }
-