diff --git a/examples/scripts/SPM_compare_particle_grid.py b/examples/scripts/SPM_compare_particle_grid.py
index 72e8b4ca18..fe2717dec3 100644
--- a/examples/scripts/SPM_compare_particle_grid.py
+++ b/examples/scripts/SPM_compare_particle_grid.py
@@ -74,7 +74,7 @@
 
 # plot
 def plot(t):
-    fig, _ = plt.subplots(figsize=(15, 8))
+    plt.subplots(figsize=(15, 8))
     plt.subplot(121)
     plt.xlabel(r"$r_n$")
     plt.ylabel("Negative particle concentration [mol.m-3]")