diff --git a/theme/openprops/system-open-props.css b/theme/openprops/system-open-props.css
index 7fa237d..6065e10 100644
--- a/theme/openprops/system-open-props.css
+++ b/theme/openprops/system-open-props.css
@@ -34,4 +34,6 @@
 	--system-invalid-color: color-mix(in oklab, var(--system-active-text) 90%, var(--system-canvas-text));
 	--system-submit-button: var(--system-accent-color);
 	--system-submit-button-text: var(--system-canvas);
+
+	--system-dimension-content-width: 80ch;
 }