diff --git a/pgrep.c b/pgrep.c
index 7a2ffb80..c8cd0cac 100644
--- a/pgrep.c
+++ b/pgrep.c
@@ -684,7 +684,7 @@ static void parse_opts (int argc, char **argv)
 //		case 'z':   // Solaris: match by zone ID
 //			break;
 		case '?':
-			usage (opt);
+			usage (optopt ? optopt : opt);
 			break;
 		}
 	}