diff --git a/swash/processing/post.py b/swash/processing/post.py
index b8e6d17..89eb669 100644
--- a/swash/processing/post.py
+++ b/swash/processing/post.py
@@ -166,8 +166,8 @@ out = pathlib.Path(config.get("post", "out")).joinpath(f"t{t0}x{x0}")
 log.info(f"Saving plots in '{out}'")
 out.mkdir(parents=True, exist_ok=True)
 
-fig.savefig(out.joinpath("t.png"))
-fig_r.savefig(out.joinpath("R.png"))
-fig_x.savefig(out.joinpath("x.png"))
+fig.savefig(out.joinpath("t.pdf"))
+fig_r.savefig(out.joinpath("R.pdf"))
+fig_x.savefig(out.joinpath("x.pdf"))
 
 log.info("Finished post-processing")