diff --git a/gpaw/README.md b/gpaw/README.md
index e69eaaaac6f33b24df7eb66ee1cb279577c4e382..3a09c793fb424df4beb7df4b547118ab3ca91020 100644
--- a/gpaw/README.md
+++ b/gpaw/README.md
@@ -104,7 +104,7 @@ GPAW_PPN=<no. of MPI tasks per node>
 For example, in a SLURM system, this could be:
 ```shell
 GPAW_PPN=12 GPAW_OFFLOAD=1 mpirun -np 256 -bootstrap slurm \
-  ./affinity-wrapper.sh gpaw-python input.py
+  ./affinity-wrapper.sh 12 gpaw-python input.py
 ```
 
 #### Examples