diff --git a/scripts/prompt_matrix.py b/scripts/prompt_matrix.py
index 4d1e152d..5fd952e9 100644
--- a/scripts/prompt_matrix.py
+++ b/scripts/prompt_matrix.py
@@ -84,6 +84,6 @@ class Script(scripts.Script):
         processed.infotexts.insert(0, processed.infotexts[0])
 
         if opts.grid_save:
-            images.save_image(processed.images[0], p.outpath_grids, "prompt_matrix", prompt=original_prompt, seed=processed.seed, grid=True, p=p)
+            images.save_image(processed.images[0], p.outpath_grids, "prompt_matrix", extension=opts.grid_format, prompt=original_prompt, seed=processed.seed, grid=True, p=p)
 
         return processed
diff --git a/scripts/xy_grid.py b/scripts/xy_grid.py
index 0f27deda..d402c281 100644
--- a/scripts/xy_grid.py
+++ b/scripts/xy_grid.py
@@ -383,6 +383,6 @@ class Script(scripts.Script):
             )
 
         if opts.grid_save:
-            images.save_image(processed.images[0], p.outpath_grids, "xy_grid", prompt=p.prompt, seed=processed.seed, grid=True, p=p)
+            images.save_image(processed.images[0], p.outpath_grids, "xy_grid", extension=opts.grid_format, prompt=p.prompt, seed=processed.seed, grid=True, p=p)
 
         return processed