diff --git a/dangerzone/cli.py b/dangerzone/cli.py
index 834499a..1718975 100644
--- a/dangerzone/cli.py
+++ b/dangerzone/cli.py
@@ -52,7 +52,7 @@ def cli_main(
             return
 
         try:
-            with open(os.path.abspath(output_filename), "rb") as f:
+            with open(os.path.abspath(output_filename), "wb"):
                 pass
         except:
             valid = False
@@ -68,7 +68,7 @@ def cli_main(
             f"{os.path.splitext(common.input_filename)[0]}-safe.pdf"
         )
         try:
-            with open(common.output_filename, "rb") as f:
+            with open(common.output_filename, "wb"):
                 pass
         except:
             click.echo(