diff -ur distcc-2.18.3/src/arg.c distcc-modified/src/arg.c
--- distcc-2.18.3/src/arg.c	2004-11-30 13:13:53.000000000 +0100
+++ distcc-modified/src/arg.c	2008-02-05 17:56:58.000000000 +0100
@@ -171,6 +171,12 @@
                     to distribute it even if we could. */
                 rs_trace("%s implies -E (maybe) and must be local", a);
                 return EXIT_DISTCC_FAILED;
+            } else if (!strcmp(a, "-march=native")) {
+                rs_trace("-march=native generates code for local machine; must be local");
+                return EXIT_DISTCC_FAILED;
+            } else if (!strcmp(a, "-mtune=native")) {
+                rs_trace("-mtune=native optimizes for local machine; must be local");
+                return EXIT_DISTCC_FAILED;
             } else if (str_startswith("-Wa,", a)) {
                 /* Look for assembler options that would produce output
                  * files and must be local.