diff --git a/lang/gcc/4.9/Makefile b/lang/gcc/4.9/Makefile
index 486b8ec4c18..836a1741978 100644
--- a/lang/gcc/4.9/Makefile
+++ b/lang/gcc/4.9/Makefile
@@ -1,4 +1,4 @@
-# $OpenBSD: Makefile,v 1.16 2015/07/19 21:22:49 pascal Exp $
+# $OpenBSD: Makefile,v 1.17 2015/08/06 18:38:34 sthen Exp $
 
 BROKEN-arm = needs binutils-2.17
 
@@ -6,6 +6,7 @@ ONLY_FOR_ARCHS = amd64 arm hppa i386 powerpc sparc sparc64
 DPB_PROPERTIES = parallel
 
 V = 4.9.3
+REVISION = 0
 FULL_VERSION = $V
 FULL_PKGVERSION = $V
 
diff --git a/lang/gcc/4.9/patches/patch-gcc_config_rs6000_rs6000_c b/lang/gcc/4.9/patches/patch-gcc_config_rs6000_rs6000_c
new file mode 100644
index 00000000000..b166dd250cd
--- /dev/null
+++ b/lang/gcc/4.9/patches/patch-gcc_config_rs6000_rs6000_c
@@ -0,0 +1,27 @@
+$OpenBSD: patch-gcc_config_rs6000_rs6000_c,v 1.1 2015/08/06 18:38:34 sthen Exp $
+
+Disable code which passes ".machine ppc" to the assembler as it breaks
+use of some CPU features. Notably breaks -maltivec which breaks build of
+Mozilla ports including xulrunner.
+
+Borrowed from https://github.com/sba1/adtools/commit/b24ae065714a2390d7718d2c348fe5cfa40c2b48
+
+--- gcc/config/rs6000/rs6000.c.orig	Wed Aug  5 20:54:32 2015
++++ gcc/config/rs6000/rs6000.c	Wed Aug  5 20:55:36 2015
+@@ -4983,6 +4983,8 @@ rs6000_file_start (void)
+   if (rs6000_default_cpu == 0 || rs6000_default_cpu[0] == '\0'
+       || !global_options_set.x_rs6000_cpu_index)
+     {
++      /* Temporarily disabled as it overrides e.g., -mcpu=440 and -maltivec */
++#if 0
+       fputs ("\t.machine ", asm_out_file);
+       if ((rs6000_isa_flags & OPTION_MASK_DIRECT_MOVE) != 0)
+ 	fputs ("power8\n", asm_out_file);
+@@ -4998,6 +5000,7 @@ rs6000_file_start (void)
+ 	fputs ("ppc64\n", asm_out_file);
+       else
+ 	fputs ("ppc\n", asm_out_file);
++#endif
+     }
+ #endif
+ }