diff --git a/src/framework/MOM_diag_buffers.F90 b/src/framework/MOM_diag_buffers.F90
index 33600dd370..d5cde56e15 100644
--- a/src/framework/MOM_diag_buffers.F90
+++ b/src/framework/MOM_diag_buffers.F90
@@ -16,6 +16,7 @@ module MOM_diag_buffers
   integer :: js !< The start slot of the array j-direction
   integer :: ie !< The end slot of the array i-direction
   integer :: je !< The end slot of the array j-direction
+  real :: fill_value = 0. !< Set the fill value to use when growing the buffer
 
   integer, allocatable, dimension(:) :: ids  !< List of diagnostic ids whose slot corresponds to the row in the buffer
   integer :: length = 0 !< The number of slots in the buffer
@@ -23,6 +24,7 @@ module MOM_diag_buffers
   contains
 
   procedure(a_grow), deferred :: grow !< Increase the size of the buffer
+  procedure, public :: set_fill_value !< Set the fill value to use when growing the buffer
   procedure, public :: check_capacity_by_id !< Check the size size of the buffer and increase if necessary
   procedure, public :: set_horizontal_extents !< Define the horizontal extents of the arrays
   procedure, public :: mark_available !< Mark that a slot in the buffer can be reused
@@ -60,6 +62,13 @@ subroutine a_grow(this)
   class(diag_buffer_base), intent(inout) :: this !< The diagnostic buffer
 end subroutine
 
+!> Set the fill value to use when growing the buffer
+subroutine set_fill_value(this, fill_value)
+  class(diag_buffer_base), intent(inout) :: this !< The diagnostic buffer
+  real,                    intent(in)    :: fill_value !< The fill value to use when growing the buffer [arbitrary]
+
+end subroutine set_fill_value
+
 !> Mark a slot in the buffer as unused based on a diagnostic id. For example,
 !! the data in that slot has already been consumed and can thus be overwritten
 subroutine mark_available(this, id)
@@ -154,7 +163,7 @@ subroutine grow_2d(this)
   call this%grow_ids()
 
   n = this%length
-  allocate(temp(n+1, this%is:this%ie, this%js:this%je), source=0.)
+  allocate(temp(n+1, this%is:this%ie, this%js:this%je), source=this%fill_value)
   if (n>0) temp(1:n,:,:) = this%buffer(:,:,:)
   call move_alloc(temp, this%buffer)
   this%length = this%length + 1
@@ -183,7 +192,7 @@ subroutine grow_3d(this)
   call this%grow_ids()
 
   n = this%length
-  allocate(temp(n+1, this%is:this%ie, this%js:this%je, this%ks:this%ke), source=0.)
+  allocate(temp(n+1, this%is:this%ie, this%js:this%je, this%ks:this%ke), source=this%fill_value)
   if (n>0) temp(1:n,:,:,:) = this%buffer(:,:,:,:)
   call move_alloc(temp, this%buffer)
   this%length = this%length + 1
diff --git a/src/framework/MOM_diag_mediator.F90 b/src/framework/MOM_diag_mediator.F90
index f0b172de91..690519a7c1 100644
--- a/src/framework/MOM_diag_mediator.F90
+++ b/src/framework/MOM_diag_mediator.F90
@@ -1109,6 +1109,7 @@ subroutine define_axes_group(diag_cs, handles, axes, nz, vertical_coordinate_num
     if (axes%is_q_point) axes%mask2d => diag_cs%mask2dBu
     call axes%buffer_2d%set_horizontal_extents(lbound(axes%mask2d,1), ubound(axes%mask2d,1), &
                                                lbound(axes%mask2d,2), ubound(axes%mask2d,2))
+    call axes%buffer_2d%set_fill_value(diag_cs%missing_value)
   endif
   ! A static 3d mask for non-native coordinates can only be setup when a grid is available
   axes%mask3d => null()
@@ -1128,6 +1129,7 @@ subroutine define_axes_group(diag_cs, handles, axes, nz, vertical_coordinate_num
     call axes%buffer_3d%set_horizontal_extents(is=lbound(axes%mask3d,1), ie=ubound(axes%mask3d,1), &
                                                js=lbound(axes%mask3d,2), je=ubound(axes%mask3d,2))
     call axes%buffer_3d%set_vertical_extent(ks=lbound(axes%mask3d,3), ke=ubound(axes%mask3d,3))
+    call axes%buffer_3d%set_fill_value(diag_cs%missing_value)
   endif
 
 
@@ -1931,7 +1933,7 @@ subroutine post_data_3d_by_point(diag_field_id, field, diag_cs, i, j, k)
 
   diag => diag_cs%diags(diag_field_id)
   buffer_slot = diag%axes%buffer_3d%find_buffer_slot(diag_field_id)
-  diag%axes%buffer_3d%buffer(buffer_slot, i, j, k) = field
+  diag%axes%buffer_3d%buffer(buffer_slot,i,j,k) = field
 end subroutine post_data_3d_by_point
 
 !> Post the final buffer using the standard post_data interface