diff --git a/src/mo_fortran_tools.F90 b/src/mo_fortran_tools.F90
index 6f9fbe45994d11ed4dc8e1053155b30cca87ce70..74e7ec76b70b1ab21d5ce840bdfab6d10701ad78 100644
--- a/src/mo_fortran_tools.F90
+++ b/src/mo_fortran_tools.F90
@@ -1201,6 +1201,7 @@ CONTAINS
 #else
 !$omp do collapse(4)
 #endif
+!NEC$ forced_collapse
     DO i4 = 1, m4
       DO i3 = 1, m3
         DO i2 = 1, m2
@@ -1235,6 +1236,7 @@ CONTAINS
 #else
 !$omp do collapse(4)
 #endif
+!NEC$ forced_collapse
     DO i4 = 1, m4
       DO i3 = 1, m3
         DO i2 = 1, m2
@@ -1269,6 +1271,7 @@ CONTAINS
 #else
 !$omp do collapse(4)
 #endif
+!NEC$ forced_collapse
     DO i4 = 1, m4
       DO i3 = 1, m3
         DO i2 = 1, m2