diff --git a/src/update_flags.h b/src/update_flags.h
index b18cabcb1b..dbbcdc98ba 100644
--- a/src/update_flags.h
+++ b/src/update_flags.h
@@ -16,11 +16,20 @@ namespace lyx {
 
 namespace Update {
 	enum flags {
+		/// No screen update is needed.
 		None = 0,
+		/// Recenter the screen around the cursor if is found outside the
+		/// visible area.
 		FitCursor = 1,
+		/// Force a full screen metrics update.
 		Force = 2,
+		/// Try to rebreak only the current paragraph metrics.
 		SinglePar = 4,
+		/// Indicate a selection that spans multiple paragraphs.
+		/// FIXME: get rid of this.
 		MultiParSel = 8,
+		/// Only the inset decorations need to be redrawn, no text metrics
+		/// update is needed.
 		Decoration = 16
 	};