diff --git a/definitions/diag/boot.def b/definitions/diag/boot.def
index f876836ee..a4b3f4eb0 100644
--- a/definitions/diag/boot.def
+++ b/definitions/diag/boot.def
@@ -1,11 +1,4 @@
 ## Copyright 2005-2019 ECMWF.
-#
-# This software is licensed under the terms of the Apache Licence Version 2.0
-# which can be obtained at http://www.apache.org/licenses/LICENSE-2.0.
-# 
-# In applying this licence, ECMWF does not waive the privileges and immunities granted to it by
-# virtue of its status as an intergovernmental organisation nor does it submit to any jurisdiction.
-#
 
 position startOfHeaders;
 ascii[4]      identifier;
diff --git a/definitions/diag/section.1.def b/definitions/diag/section.1.def
index 25487a043..1fd931c43 100644
--- a/definitions/diag/section.1.def
+++ b/definitions/diag/section.1.def
@@ -1,11 +1,4 @@
 # Copyright 2005-2019 ECMWF.
-#
-# This software is licensed under the terms of the Apache Licence Version 2.0
-# which can be obtained at http://www.apache.org/licenses/LICENSE-2.0.
-# 
-# In applying this licence, ECMWF does not waive the privileges and immunities granted to it by
-# virtue of its status as an intergovernmental organisation nor does it submit to any jurisdiction.
-#
 
 section_length[3] section1Length ;
 
@@ -27,23 +20,12 @@ codetable[1] indicatorOfTypeOfLevel 'grib1/3.table';
 codetable[2] heightPressureEtcOfLevels 'grib1/3.table';
 alias ls.levelType=indicatorOfTypeOfLevel;
 
-#  Year of century
-# NOTE 6 NOT FOUND
 unsigned[1] yearOfCentury ;
-
-#  Month
 unsigned[1] month ;
-
-#  Day
 unsigned[1] day;
-
-#  Hour
 unsigned[1] hour ;
-
-#  Minute
 unsigned[1] minute ;
 
-
 transient second  = 0;
 meta      dataDate    budgdate(yearOfCentury,month,day);
 alias ls.date=dataDate;
@@ -51,21 +33,16 @@ meta      dataTime    time(hour,minute,second);
 alias ls.time=dataTime;
 meta julianDay julian_day(dataDate,hour,minute,second) : edition_specific;
 
-
-#  Indicator of unit of time range
+# Indicator of unit of time range
 codetable[1] indicatorOfUnitOfTimeRange 'grib1/4.table';
 
-#  P1 - Period of time
-# (number of time units)
+# P1 - Period of time (number of time units)
 unsigned[1] periodOfTime ;
+alias P1 =  periodOfTime ;
 
-alias   P1 =  periodOfTime ;
-
-#  P2 - Period of time
-# (number of time units)
+# P2 - Period of time
 unsigned[1] periodOfTimeIntervals ;
-
-alias   P2 =  periodOfTimeIntervals ;
+alias P2 =  periodOfTimeIntervals ;
 
 codetable[1] timeRangeIndicator 'grib1/5.table';
 
diff --git a/definitions/diag/section.4.def b/definitions/diag/section.4.def
index 2dbbab699..9a4887349 100644
--- a/definitions/diag/section.4.def
+++ b/definitions/diag/section.4.def
@@ -1,18 +1,9 @@
 # Copyright 2005-2019 ECMWF.
-#
-# This software is licensed under the terms of the Apache Licence Version 2.0
-# which can be obtained at http://www.apache.org/licenses/LICENSE-2.0.
-# 
-# In applying this licence, ECMWF does not waive the privileges and immunities granted to it by
-# virtue of its status as an intergovernmental organisation nor does it submit to any jurisdiction.
-#
 
 section_length[3] section4Length ;
 
 unsigned[1] reserved1=0 : hidden;
-
 flags[1] missingDataFlag 'grib1/1.table';
-
 unsigned[1] numberOfBytesPerInteger=4;
 
 unsigned[2] reserved=0 : hidden ;
@@ -26,9 +17,7 @@ unsigned[3] numberOfIntegers=0;
 alias numberOfInts=numberOfIntegers ;
 
 unsigned[3] numberOfLogicals ;
-
 unsigned[3] numberOfReservedBytes ;
-
 unsigned[4] reserved=0 : hidden;
 unsigned[4] reserved=0 : hidden;
 unsigned[1] reserved=0 : hidden;
@@ -36,18 +25,18 @@ unsigned[1] reserved=0 : hidden;
 ibmfloat floatValues[numberOfFloats];
 alias floatVal=floatValues;
 
-if(numberOfIntegers) {
+if (numberOfIntegers) {
   signed[4] integerValues[numberOfIntegers];
 }
 
-#if(numberOfBytesPerInteger == 1) { signed[1] integerValues[numberOfIntegers]; }
-#if(numberOfBytesPerInteger == 2) { signed[2] integerValues[numberOfIntegers]; }
-#if(numberOfBytesPerInteger == 3) { signed[3] integerValues[numberOfIntegers]; }
-#if(numberOfBytesPerInteger == 4) { signed[4] integerValues[numberOfIntegers]; }
-
-charValues list(numberOfCharacters) {
-    ascii[1] char;
+# TODO: temporary solution for variable-length list of ascii
+#charValues list(numberOfCharacters) {
+#    ascii[1] char;
+#}
+if (numberOfCharacters) {
+  unsigned[1] charValues[numberOfCharacters];
+  alias charVal=charValues;
 }
-alias charVal=charValues;
 
+# Final padding
 section_padding padding;