Index: usr.bin/dtc/dtc.cc
===================================================================
--- usr.bin/dtc/dtc.cc
+++ usr.bin/dtc/dtc.cc
@@ -294,7 +294,10 @@
 			}
 			break;
 		default:
-			fprintf(stderr, "Unknown option %c\n", ch);
+			/* 
+			 * Since opterr is non-zero, getopt will have
+			 * already printed an error message.
+			 */
 			return EXIT_FAILURE;
 		}
 	}