diff -Naur rcs-5.7.orig/src/rcsdiff.c rcs-5.7/src/rcsdiff.c
--- rcs-5.7.orig/src/rcsdiff.c	1995-06-16 16:19:24.000000000 +1000
+++ rcs-5.7/src/rcsdiff.c	2007-07-19 11:56:21.000000000 +1000
@@ -214,7 +214,7 @@
 	    case '-': case 'D':
 		    no_diff_means_no_output = false;
 		    /* fall into */
-	    case 'C': case 'F': case 'I': case 'L': case 'W':
+	    case 'C': case 'F': case 'I': case 'L': case 'U': case 'W':
 #if DIFF_L
 		    if (c == 'L'  &&  ++file_labels == 2)
 			faterror("too many -L options");