diff --git a/src/MNH/write_aircraft_balloon.f90 b/src/MNH/write_aircraft_balloon.f90
index 90e246ab7f20783b8c8f670dd1f8b3b1011f596f..913947e848a909241f721c412479f74d181dbb6d 100644
--- a/src/MNH/write_aircraft_balloon.f90
+++ b/src/MNH/write_aircraft_balloon.f90
@@ -65,7 +65,7 @@ END MODULE MODI_WRITE_AIRCRAFT_BALLOON
 !!  Philippe Wautelet: 05/2016-04/2018: new data structures and calls for I/O
 !  P. Wautelet 29/01/2019: bug: moved an instruction later (to prevent access to a not allocated array)
 !  P. Wautelet 13/09/2019: budget: simplify and modernize date/time management
-!
+!  P. Wautelet 02/10/2020: bugfix: YGROUP/YGROUPZ were too small
 ! --------------------------------------------------------------------------
 !
 !*      0. DECLARATIONS
@@ -186,7 +186,7 @@ REAL, DIMENSION(:,:,:,:,:),   ALLOCATABLE :: ZPTOTA
 REAL, DIMENSION(:,:,:),       ALLOCATABLE :: ZRHO
 !
 INTEGER, DIMENSION(:),            ALLOCATABLE :: IGRID    ! grid indicator
-CHARACTER(LEN=  8)                            :: YGROUP   ! group title
+CHARACTER(LEN=:), ALLOCATABLE                 :: YGROUP   ! group title
 CHARACTER(LEN=100), DIMENSION(:), ALLOCATABLE :: YCOMMENT ! comment string
 CHARACTER(LEN=100), DIMENSION(:), ALLOCATABLE :: YTITLE   ! title
 CHARACTER(LEN=100), DIMENSION(:), ALLOCATABLE :: YUNIT    ! physical unit
@@ -194,7 +194,7 @@ CHARACTER(LEN=100), DIMENSION(:), ALLOCATABLE :: YUNIT    ! physical unit
 INTEGER :: IPROC    ! number of variables records
 INTEGER :: JPROC    ! loop counter
 INTEGER, DIMENSION(:),            ALLOCATABLE :: IGRIDZ   ! grid indicator
-CHARACTER(LEN=  8)                            :: YGROUPZ  ! group title
+CHARACTER(LEN=:), ALLOCATABLE                 :: YGROUPZ  ! group title
 CHARACTER(LEN=100), DIMENSION(:), ALLOCATABLE :: YCOMMENTZ! comment string
 CHARACTER(LEN=100), DIMENSION(:), ALLOCATABLE :: YTITLEZ  ! title
 CHARACTER(LEN=100), DIMENSION(:), ALLOCATABLE :: YUNITZ   ! physical unit