diff --git a/src/pysource/fields.py b/src/pysource/fields.py
index 88de91533..be3a6e4ef 100644
--- a/src/pysource/fields.py
+++ b/src/pysource/fields.py
@@ -129,7 +129,7 @@ def wavefield_subsampled(model, u, nt, t_sub, space_order=8):
     if t_sub > 1:
         time_subsampled = ConditionalDimension(name='t_sub', parent=model.grid.time_dim,
                                                factor=t_sub)
-        nsave = (nt+t_sub-1)//t_sub
+        nsave = nt // t_sub + 1
     else:
         return None
     wf_s = []