BR3104852: only warn once for repeated prefixes
diff --git a/parser.c b/parser.c
index 681aa39..42ac109 100644
--- a/parser.c
+++ b/parser.c
@@ -292,7 +292,7 @@
             int slot = prefix_slot(tokval.t_integer);
             if (result->prefixes[slot]) {
                if (result->prefixes[slot] == tokval.t_integer)
-                    nasm_error(ERR_WARNING,
+                    nasm_error(ERR_WARNING | ERR_PASS1,
                                "instruction has redundant prefixes");
                else
                     nasm_error(ERR_NONFATAL,