diff --git a/d4tools/src/plot/cli.yml b/d4tools/src/plot/cli.yml
index 76d9097..27727ed 100644
--- a/d4tools/src/plot/cli.yml
+++ b/d4tools/src/plot/cli.yml
@@ -14,6 +14,7 @@ args:
         short: R
         long: resolution
         help: Specify the resolution of the output image
+        value_name: widthxheight
     - region:
         required: true
         short: r